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  • 1. P7 Physics ‘triple science’ Route map Over the next 24 lessons you will study: Friday 21 October 2011 P7.1 What is a telescope P7.2 Describing lenses P7.3 Refracting telescopes P7.4 Reflecting telescopes P7.5 Radio telescopes P7.7 Images of stars P7.8 The Sun, Moon and Earth P7.9 Observing the skies P7.10 Eclipses P7.11 Star distances P7.12 Star brightness P7.6 Ray diagrams P7.14 Galaxies-cepheid variable stars P7.15 Galaxies one or many P7.13 Star temperatures P7.16 Mapping the Milky Way P7.17 The changing Universe P7.18 Our Sun P7.19 The composition of stars P7.20 Emission spectra P7.21 Atoms and nuclei P7.22 Nuclear fusion P7.23 Behaviour of gases part one P7.24 Behaviour of gases part two P7.25 Types of stars P7.26 Structure of our Sun End of module test P7.27 Protostars P7.28 Star death
  • 2. P7.1 What is a telescope ? Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand how a variety of telescopes have been developed through history.
    • Understand the different images produced by telescopes and understand that images can be produced from electromagnetic radiation of different frequencies.
    We will focus on. Friday 21 October 2011 First activity: Telescopes can detect electromagnetic radiation to produce an image. How many different types of electromagnetic radiation can you remember ? Can you list them all in order of their wavelength tarting with gamma rays first ? Literacy: Telescope, reflection, refraction, electromagnetic spectrum, astronomy, universe, image, lenses, focus and electromagnetic radiation. Numeracy: The Hubble telescope’s two mirrors are a near perfect curve. If Hubble's primary mirror were scaled up to the diameter of the Earth, the largest imperfection would be only 15 cm tall. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
  • 3. Extension questions: 1: What is the purpose of the lens in a telescope ? 2: A large number of telescopes use large polished curved mirrors, what is the purpose of these mirrors ? 3: Why do you think knowledge and understanding of the Universe and our own Solar System improved greatly after the 1930’s ? 4: Why do you think a large range of telescopes with very different size and shape dishes have been developed ? 5: Explain why you should never observe the Sun using a telescope ? Know this: a: Know that a large range of types of telescope have been developed. b: Know that telescopes can produce images using different frequencies of electromagnetic radiation. Friday 21 October 2011 Introduction: In the Autumn of 1609 Galileo made his first observations of the moon using a telescope, although he was not the first person to use a telescope, his observations had a huge impact and changed the way people see the universe. In the 1930’s astronomers discovered that objects in the universe produced radiation other than just visible light. Since then, a large range of telescopes have now been developed, to produce images using different types of electromagnetic radiation, for example X-rays and Infra red. The radiation traveling from distant stars and galaxies takes and extremely long time to react the Earth, so looking at these images is like looking back in time ! P7.1 What is a telescope ?
  • 4. Key concepts P7.1 a Look at the photograph and information and answer all the questions: principal axis object image A refracting telescope works by having two converging lenses of different powers set in line with each other. The lenses can be moved towards or away from each other to focus the image. The smaller lens is called the eyepiece and the larger lens is called the objective lens. The light gathering power of the telescope is given by D which is the diameter of the lens. Why is it necessary to be able to move the two lenses towards or away from each other in a simple telescope ? Look at the ray diagram above, why is the image produced by a refracting telescope inverted and smaller than the real object ? A reflecting telescope
  • 5. Key concepts P7.1 b Look at the photograph and information and answer all the questions: object image Inside a simple reflecting telescope The reflecting telescope designed by Isaac Newton has a large concave mirror to collect reflected light from a distant object like a planet in our solar system. The concave mirror also converges the light to a small plane mirror for the observers eye. The eye lens acts like a magnifying glass to increase the size of the virtual image. In all telescopes the mirror is made from silvered glass...explain why this has to be as smooth as possible ? Saturn or any other planet does not produce its own light...explain where the light comes from that we use to view these planets ?
  • 6. Key concepts P7.1 c Look at the photograph and information and answer all the questions: Explain why this single picture taken over 10 days in 1998 has radically change the way we view our own Universe ? It is estimated that some of the galaxies picture above are up to 13 billion light years away. Explain why if life does exist there we may never know of its existence ? The Hubble telescope launched in 1996 by the shuttle program is in a fixed orbit outside the Earth’s atmosphere. In order to take images of distant, faint objects, Hubble must be extremely steady and accurate. The telescope is able to lock onto a target without deviating more than 7/1000 th of an arc-second, or about the width of a human hair seen at a distance of 1 mile. Hubble ‘deep space’ photograph in 1998 At Christmas, in 1998 Hubble’s camera was pointed at an area of space with no visible features for 10 days. When the picture was sent to Earth it showed that this small part of deep space was full of galaxies. Each speck on the picture right is a galaxy containing up to 100 billion stars
  • 7. P7.1 Plenary Lesson summary: x-rays universe visible gamma Friday 21 October 2011 In 1609 Galileo made his first observations of the moon using a telescope. His further work placed the sun at the centre of our solar system not Earth as was taught by the bible. In deeply religious and catholic Italy Galileo was arrested and tortured by the Vatican until he renounced his findings. How Science Works: Research into how light is affected by passing through lenses. Look into different types of lenses using the terms focal length and power. If you wear glasses, find out how strong they are in dioptres. Preparing for the next lesson: Telescopes make things _________ that cannot been seen with the naked eye. A large range of telescopes have been developed to produce images of the ________ using not only light, but also radio waves, ________, infra red and _______ radiation. Decide whether the following statements are true or false : False True 3: Most telescopes only detect visible light ? False True 2: We cannot see anything in the Universe without the use of a telescope ? False True 1: Pulsars were discovered by detecting regular pulses of radio waves ?
  • 8. P7.2 Describing lenses Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand how converging lenses focus parallel rays of light and what is meant by the terms focal length and power of a lens.
    • Understand how telescope use lenses to magnify and focus incoming rays from a distant object.
    We will focus on. Friday 21 October 2011 First activity: Name four different types of electromagnetic radiation that can be used by telescopes to produced and image of the universe, for example visible light ? Literacy: Lenses, lens, convex lens, concave lens, refraction, converging lens, diverging lens, focus, focal length, focal point, principle axis, power, dioptre and normal. Numeracy: The power of a lens is inversely proportional to the focal length, as the power of the lens increases the focal length decreases. This relationship is shown by the formula power = 1/ focal length. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
  • 9. Extension questions: 1: Explain the difference between a convex and concave lens ? 2: What is the a) ‘normal’ and b) ‘principle axis’ of a lens ? 3: Which way up is the image produced by a converging lens ? 4: Explain or give three differences between the object and its image produced by a converging lens ? 5. If a light ray hits a glass lens straight on (0 degrees to the normal), there is no refraction, can you explain why ? Know this: a: Know a lens that can bend parallel light rays into a single point is called a converging lens. b: Know the link between the focal length and power of lens. Friday 21 October 2011 Introduction: The earliest and simplest telescopes used lenses to magnify and focus incoming light rays from a distant object to produce a crisp image. A lens that can focus parallel light rays into a single point is called a converging lens. Light bends as it passes through the lens, this is called refraction. A refracting telescopes uses lenses to gather and bend light as it passes though the telescope to the observer. The point at which the light rays meet in a single point is called the focus. Converging lenses can be fat or thin, the fatter a lens, the more it will refract (bend) the light as it passes through it. A fat lens that can bend light a lot is said to have a high power. Converging lenses are also used in glasses for people who are long sighted, they bring distant objects into sharper focus. P7.2 Describing lenses
  • 10. Key concepts P7.2 a Look at the photograph and information and answer all the questions: Explain what happens to the light as it travels through the glass lenses a) at region A b) in the middle at region B and c) in region C ? What happens to the speed of light as a) it travels through the glass and b) as it leaves the glass and travels through he air ? Lenses found in optical equipment including cameras, telescopes and even the human eye are able refract or bend light. Only converging or convex lenses are able to form a sharp virtual image. Images can be magnified larger than the actual object or diminished smaller than the object, depending on the type of lens that you use. Devices that use convex lenses include microscopes, zoom cameras and vision glasses. How do converging lenses work A B C
  • 11. Key concepts P7.2 b Look at the photograph and information and answer all the questions: principal axis object
    • Image
    • virtual
    • smaller
    • upside down
    focal length cm Look at the ray diagram. To increase the focal length would you have to use a fatter or thinner lens ? If the lens surface is scratched or bumpy, what would happen to the image produced ? The ray diagram above shows how a converging lens bends light rays to meet at a point called the focus. The distance from the centre of the lens to the focus is called the focal length. This can be measured in millimetres or centimetres. A thin lens will have a long focal length and a fat lens will have a shorter focal length. How an image is produced using a converging lens
  • 12. Key concepts P7.2 c Look at the photograph and information and answer all the questions: Lenses of different thicknesses can bend light by different amounts. They each have a different focal length. A fat lens bends light a lot, it is said to have a high power, and a short focal length. The higher the power of a lens, the shorter the focal length. The power of a lens is measured in dioptres (D). The strength of the lens found in the human eye is about 33 dioptres ! Which has a longer focal length, a pair of reading glasses with lenses of power +2.5 D or a pair labelled as power +0.5 D ? What is a) the power of a lens with a focal length of 50 cm (hint – look at units!) and b) What is the focal length of a lens with a power of +4.5 D ? Focal length and converging lenses focal length focal length focal length
  • 13. P7.2 Plenary Lesson summary: refraction shorter dioptres power Friday 21 October 2011 Reflector telescopes are used not only to examine the visible region but also to explore both the shorter- and longer-wavelength regions (i.e., UV and IR). The name of this type of instrument is derived from the fact that the primary mirror reflects the light back to a focus instead of refracting it. The primary mirror usually has a concave spherical or parabolic shape, and, as it reflects the light, it inverts the image at the focal plane. How Science Works: Research into how refracting telescopes work to produce an image and look into how the aperture of the main lens determines a telescope’s magnifying ability. Preparing for the next lesson: A converging lens bends light to a point called a focus in order to produce an image. The bending of the light is called __________. The _________ of a lens is measured in units called__________. The Higher the power of a lens, the _________ the focal length will be. Decide whether the following statements are true or false : False True 3: Light is refracted by a lens because the lens slows down the light rays ? False True 2: Power of a lens = 1 x focal length of the lens ? False True 1: A low power lens will have a short focal length compared to a high power lens ?
  • 14. P7.3 Refracting Telescopes Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand how converging lenses are used in telescopes to produce an image
    • Understand how lenses are used to magnify a distant object like a planet
    • Understand how bigger apertures give brighter images in telescopes.
    We will focus on. Friday 21 October 2011 First activity: Think back to last lesson on describing lenses, can you write a definition of a converging lens ? Literacy: Refraction, lens, telescope, refractor, eye piece lens, objective lens, diverging lens, converging lens, convex, biconvex and aperture. Numeracy: With the naked eye, it is possible to see about 3000 stars in the night sky. Using a simple optical telescope it is possible to see about 30,000 stars in the night sky ! PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
  • 15. Extension questions: 1: Why are the lenses used in telescopes described as ‘biconvex’? 2: What are the names of the two refracting lenses used in a telescope? 3: Why do you think refracting lenses were used in spectacles for hundreds of years before they were first used in a telescope? 4: Why do the two lenses in a telescope need to be different powers? Know this: a: Know that a simple telescope can be made by looking through two converging lenses positioned one in front of the other. b: Know that a large aperture produces a better image Friday 21 October 2011 Introduction: Any converging lens can act as a magnifying glass and make an object appear larger. The telescope was invented by Hans Lippershey when he watched his young children playing with lenses. He realised that by looking through two converging lenses far away objects appeared bigger and closer. A refracting telescope has two lenses, an eye piece lens and an objective lens. Moving the to lenses either closer to each other or further apart brings the image into focus. Binoculars also work in this way. P7.3 Refracting Telescopes
  • 16. Key concepts P7.3 a Look at the photograph and information and answer all the questions: principal axis object image A refracting telescope works by having two converging lenses of different powers set in line with each other. The lenses can be moved towards or away from each other to focus the image. The smaller lens is called the eyepiece and the larger lens is called the objective lens. The light gathering power of the telescope is given by D which is the diameter of the lens. Why is it necessary to be able to move the two lenses towards or away from each other in a simple telelscope ? Look at the ray diagram above, why is the image produced by a refracting telescope inverted and smaller than the real object ? Inside a simple reflecting telescope Lenses can be moved
  • 17. Key concepts P7.3 b Look at the photograph and information and answer all the questions: The single most important specification for any astronomical telescope is its aperture. This term refers to the diameter of the telescope's main optical lens. A telescope's aperture relates directly to the two vital aspects of the scope's performance: its light-gathering power (which determines how bright objects viewed in the scope will appear), and its maximum resolving power (how much fine detail it can reveal). Aperture and reflecting telescopes object object image image D1 = 10 cm D2 = 2 cm D3 = 6 cm D4 = 1.5 cm D3 D3 D1 D2
    • In the first telescope the magnifying power is worked out by dividing the diameter (cm) of the first and second lens....10/2 = 5 times.
    • Work out the magnifying power of the second telescope
    • Which telescope will produce the a) larger image and b) the brighter image of the object ?
  • 18. Key concepts P7.3 c Look at the photograph and information and answer all the questions: Explain how each telescope make the empire state building appear 5, 10 or 20 times closer ? Explain why with telescopes with magnifications over 10 times, a tripod is normally required to view the image ? Telescopes magnify distant objects like the empire state building so an observer can see an enlarged image. The user of the telescope also has to focus the image by moving either of the two converging lenses so the two lenses are the correct distance apart to produce a clear image. This is why telescopes and binocular are made to adjust the distance between both lenses. Magnification and telescopes x 5 magnification x 10 magnification x 20 magnification
  • 19. P7.3 Plenary Lesson summary: aperture image converging distance Friday 21 October 2011 A Dutch optician (someone who makes lenses for glasses), Hans Lippershey, designed the convex lens for the first refracting telescope in 1608. He found that a distant object appeared to be much closer when he looked at it through a concave lens and a convex lens held in front of each other. He put the lenses into a tube to make the first refracting telescope. How Science Works: Research into reflecting telescopes, how a mirror or a lens can be used to produce an image and look into wavelength and diffraction of light . Preparing for the next lesson: A refracting telescope uses two __________ lenses to produced a magnified ________. The two lenses must be the correct _________ apart to produce an in focus image. A large _________ allows more light to enter the telescope so dim stars can be seen more clearly. Decide whether the following statements are true or false : False True 3: The smaller the aperture, the better or brighter the image seen ? False True 2: The lens nearest the eye is called the objective lens ? False True 1: A telescope with two identical power lenses will not work ?
  • 20. P7.4 Reflecting telescopes Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand how mirrors collect light in reflecting telescopes
    • Understand the advantages of reflecting telescopes over refracting telescopes.
    • Understand how by reducing diffraction an image with higher resolution is produced
    We will focus on. Friday 21 October 2011 First activity: Reflecting telescopes uses a large concave mirror to collect light rays form a distant object. Explain why an image produced by a reflecting telescope with a large mirror is better when compared to an image produce using lenses in a refracting telescope ? Literacy: Reflector, diffraction, parabolic mirror, objective, resolving power, resolution, prism, plane mirror, focus, aperture, refracting telescope, reflecting telescope. Numeracy: The World’s most famous reflecting telescope today is the Hubble Space Telescope. Every 97 minutes, Hubble completes a spin around Earth, moving at the speed of about 8 kilometres per second— fast enough to travel across the United States in about 10 minutes ! PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
  • 21. Extension questions: 1:What is the name given to a curved mirror that can focus light into a single point ? 2: Why is it not possible to make a refracting telescope with a huge aperture and two very large lenses to focus the light gathered ? 3: A reflecting telescope still uses one small converging lens in the eyepiece, what is the purpose of this eye lens ? 4: Why do converging lenses ‘bend’ different colours of light by different amounts ? Know this: a: Know how a parabolic mirror can collect focus light into a single point. b: Know the advantages of using a reflecting telescope rather than a reflecting telescope. Friday 21 October 2011 Introduction: Not all telescopes use lenses, reflecting telescopes use mirrors to gather light. People often mistakenly believe that a telescope's power lies in its ability to magnify objects. Telescopes actually work by collecting more light than the human eye can capture on its own. The larger a telescope's aperture, the more light it can collect, and the better the image produced. Reflecting telescopes have many advantages over refracting telescopes. Lenses cannot be made larger than 1m in diameter or they begin to distort, but a mirror in a reflecting telescope can be made up to 10m in diameter. This means they can collect more light and produce better images of very dim and distant objects in the Uuniverse. P7.4 Reflecting telescopes
  • 22. Key concepts P7.4 a Look at the photograph and information and answer all the questions: object image Inside a simple reflecting telescope The parabolic mirror used in a reflecting telescope has many advantages over the glass lens, it can be made much larger so that it can gather more light and therefore produce better images of dim stars. It is also is much easier to produce a large mirror with no imperfections than a large lens. Lenses cannot be made larger than one metre in diameter or the shape would distort under its own weight. Compare the two ray diagrams of a parabolic mirror and a glass lens, it what way are they similar ? Give two advantages when using reflecting telescopes rather than using refracting telescopes ?
  • 23. Look at the photograph and information and answer all the questions: The reflecting telescope designed by Isaac Newton has a large concave mirror to collect reflected light from a distant object like a planet in our solar system. The concave mirror also converges the light to a small plane mirror for the observers eye. The eye lens acts like a magnifying glass to increase the size of the virtual image. In all telescopes the mirror is made from silvered glass...explain why this has to be as smooth as possible ? Saturn or any other planet does not produce its own light...explain where the light comes from that we use to view these planets ? The moon (pictured below right) can be seen using binoculars...explain why you need a telescope to view the planets like Mars and Venus ? A reflecting telescope Key concepts P7.4 b
  • 24. Key concepts P7.4 c Look at the photograph and information and answer all the questions: Look at the pros and cons of using either a reflecting or refracting telescope, which one would you buy and why ? Which type of telescope is used to image the very distant corners of the Universe ? Refracting telescopes are simpler than reflecting telescopes, but they have an important limitation. Remember that the light passing through the glass lens gets bent. It turns out that different colours are bent different amounts, and that causes the light to become unfocused. Isaac Newton solved this problem by replacing the lenses with mirrors. Against using reflecting For using reflecting Where do you place the observer and the small plane mirror. These can interfere with the image Larger mirrors give brighter images and are cheaper to produce and colour are not distorted For using refracting Lenses can only be one metre in diameter and are expensive to produce and colours are distorted The observer does not interfere with the image pathway through the telescope Against using refracting Which telescope ?
  • 25. Key concepts P7.4 d Look at the photograph and information and answer all the questions: The single most important specification for any astronomical telescope is its aperture. This term refers to the diameter of the telescope's main optical lens. A telescope's aperture relates directly to the two vital aspects of the scope's performance: its light-gathering power (which determines how bright objects viewed in the scope will appear), and its maximum resolving power (how much fine detail it can reveal). image image
    • In the first telescope the magnifying power is worked out by dividing the diameter of the first and second lens....10/2 = 5 times.
    • Work out the magnifying power of the second telescope
    • Which telescope will produce the a) larger image and b) the brighter image of the object ?
    object object Understanding a telescope’s aperture
  • 26. Key concepts P7.4 e Look at the photograph and information and answer all the questions: Explain why resolution is important when looking at stars in the night sky ? Explain why reflecting telescope suffer less from poor resolution when compared to refraction telescopes ? The larger a telescope's aperture, the greater its ability to show two adjacent stars as separate, distinct images, rather than overlapping. Large aperture telescopes also gives a brighter image, because it allows more light in. The distortion affect as shown by the two telescopes above is greatest when the aperture is small. Which telescope ? large aperture small aperture clear image blurred dim image
  • 27. P7.4 Plenary Lesson summary: mirror images lenses Reflecting Friday 21 October 2011 Reflecting telescopes have a number of other advantages over refractors. They are not subject to chromatic aberration because large blemish free mirrors are easier to produce when compared to larges lenses. Also, the telescope tube of a reflector is shorter than that of a refractor of the same diameter, which reduces the cost the telescope's manufacture. How Science Works: Research into how larger telescopes can be used to collect data from the far reaches of the Universe and look into how radio-telescopes are used to image distance nebulae and galaxies. Preparing for the next lesson: ___________ telescopes use a parabolic __________ to focus light gathered rather than a lens. Mirrors can be made much larger than __________ so a reflecting telescope can gather more light and produce better __________ of dim and distant objects in the universe. Decide whether the following statements are true or false : False True 3: The smaller the aperture of a telescope, the better the image quality? False True 2: Refracting telescopes produce better images than reflecting telescopes? False True 1: A mirror that can focus light into a point is called a parabolic mirror?
  • 28. P7.5 Radio telescopes Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand the engineering of large radio telescopes.
    • Understand how data is collected form distant galaxies by radio telescopes.
    We will focus on. Friday 21 October 2011 First activity: Draw a ray diagram to show what happens when parallel rays of light hit a parabolic mirror as is found in large diameter radio telescopes ? Literacy: Resolving power, wavelength, diffraction, parabolic mirror, objective, resolution, prism, plane mirror, focus, aperture, refracting telescope, reflecting telescope. Numeracy: Radio waves have a very long wavelength anywhere from1 mm to 30 metres so a very large parabolic reflector is needed. A radio telescope dish can be up to 80 metres in diameter ! PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
  • 29. Extension questions: 1: Radio telescopes often have very large diameters, up to 80 metres. Explain why the reflecting surface of a radio telescope does not need to made from glass ? 2: Explain why engineers have to design radio telescopes that will withstand high and low temperatures ? 3: Explain why a radio telescope’s base has to be heavy and stable ? 4: Put these telescopes in order of aperture size, light telescope, radio telescope, infra red telescope ? Know this: a: Know that engineers have to overcome many technological problems designing large diameter radio telescopes. b: Know that data is collected from distant galaxies by gathering radio waves Friday 21 October 2011 Introduction: Radio telescopes are used to study naturally occurring radio emission from stars, galaxies, quasars, and other astronomical objects between wavelengths of about 10 meters and 1 millimetre. Radio telescopes all have two basic components: (one) a large radio antenna and (two) a sensitive radiometer or radio receiver. The sensitivity of a radio telescope--i.e., the ability to measure weak sources of radio emission form a distant galaxy--depends on the its area or size and the sensitivity of the radio receiver used to amplify and detect the signals. Radio telescopes are often very large because the galaxies are other that emit the radio waves they collect are very far away for Earth P7.5 Radio telescopes
  • 30. P7.5 Radio telescopes Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand that a large aperture gives telescopes a higher resolving power .
    • Understand to reduce diffraction and produce a sharp image the aperture size must be longer than the wavelength of the radiation gathered by the telescope.
    Friday 21 October 2011 First activity: Draw a ray diagram to show what happens when parallel rays of light hit a parabolic mirror ? Literacy: Resolving power, wavelength, diffraction, parabolic mirror, objective, resolution, prism, plane mirror, focus, aperture, refracting telescope, reflecting telescope. Numeracy: Radio waves have a very long wavelength so a very large parabolic reflector is needed. A radio telescope dish can be up to 80 metres in diameter! PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
  • 31. Look at the photograph and information and answer all the questions: Radio telescopes like those pictured opposite left constantly scan deep space for electromagnetic radio waves coming from distant stars and far away galaxies. SETI (search for extraterrestrial intelligence) has been funded to look for sign of intelligent life over the last 40 years. So far they have been unsuccessful ! Do you think we will find evidence of extraterrestrial life somewhere in our own galaxy ? Compare a typical refracting telescope made form two convex lenses and a radio telescope ? Explain why the diameter of the radio telescope's dish has to be a ) l;arge and b) engineer not to distort during daily or seasonal air temperature changes ? How radio telescopes work Key concepts P7.5 a
  • 32. Key concepts P7.5 b Look at the photograph and information and answer all the questions: Although it does look like much, because of the low resolution image formed by a radio telescope, TU24 could not have been tracked using a light telescope...why ? Why do scientists want to know the path of asteroids that pass close by to Earth ? In 2007, an asteroid numbered TU24 passed by close to Earth. The space rock, estimated to be about 250 meters across, coasted by just outside the orbit of Earth's Moon. Were TU24 to have struck land, it might have caused a magnitude seven earthquake and left a city-sized crater. Its journey near to the Moon was tracked by a radio telescope. Tracking TU24 using a radio telescope ? Asteroid TU24
  • 33. Key concepts P7.5 c Look at the photograph and information and answer all the questions: Look at the five different way that the crab nebula is imaged (optical, UV, infra red, X-ray and radio waves. Are there any similarities or differences in the images ? Which type of image shows the most detail of what’s going on inside the crab nebula and explain your answer ? The Crab Nebula's creation was witnessed in 1054 A.D. when Chinese astronomers recorded its appearance. Scientists now believe the Crab Nebula is the remains of a star which suffered a supernova explosion just months after the Chinese first observe the dying star. In the nebulous cloud of gases, the rotating neutron star, or pulsar, continues to generate strobe-like pulses that can be observed at radio, optical, and X-ray energies. Crab nebula optical Infra red radio waves UV X-ray
  • 34. P7.5 Plenary Lesson summary: focus diameter metal galaxies Friday 21 October 2011 The most familiar type of radio telescope is the radio reflector consisting of a parabolic antenna--the so-called dish or filled-aperture telescope--which operates in the same manner as a television-satellite receiving antenna to focus the incoming radiation onto a small antenna referred to as the feed, a term that originated with antennas used for radar transmissions. How Science Works: Research into how to show light rays travelling through refracting and reflecting telescopes. Look into the laws of reflection and refraction Preparing for the next lesson: A radio telescope use a large _________ parabolic _____ dish to collect and ______ radio waves with wavelengths between 1 mm and 30 cm. This radio waves are emitted by and travel huge distances across the Universe form very distant ________. Decide whether the following statements are true or false : False True 3: Radio telescopes do not have mirrors or lenses ? False True 2: A optical telescope has a smaller aperture than a radio telescope ? False True 1: Telescope with large apertures have higher resolving powers ?
  • 35. P7.6 Ray diagrams Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand how to draw a ray diagram for light reflected from a parabolic mirror.
    • Understand how to draw ray diagrams for light passing through a converging lens.
    Friday 21 October 2011 First activity: Think about refraction where light slows down as it passes through air to another medium like glass or water. Give three examples where you see refraction of light happening ? Numeracy: Light travels at 300,000 kms -1 through air but through glass it slows to 240,000 kms -1 . When its slows light bends towards the normal. When light leaves the lens to travel through air it speeds up again and bends back toward the normal . PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers Literacy: Reflector, diffraction, parabolic mirror, objective, resolving power, resolution, prism, plane mirror, focus, aperture, refracting telescope, reflecting telescope.
  • 36. Extension questions: 1: Two converging lenses. Lens one has twice the focal length (cm) when compared to lens two. Which is the stronger lens ? 2: Explain why diverging lenses are not found in simple refracting telescopes ? 3: Draw two converging lenses and show how three light rays form a focal point. Lens one has a focal length of 3 cm and lens two has a focal length of 8 cm ? 4: How does a refracting telescope focus its image of a distant star ? Know this: a: Know how to draw a ray diagram from light reflected from a parabolic mirror. b: Know how to draw a ray diagram for light pass through converging lenses. Friday 21 October 2011 Introduction: When light strikes a reflecting or refracting surface of a telescope from a distant star, the light can be regarded as parallel. In reflecting telescopes, the parallel rays of light are focused by a parabolic mirror. Each ray coming in observes the ‘law of reflection’ and as such the rays are focussed where they are collected by a mobile detector In refracting telescopes, the parallel light rays enter the lens from a distant star. An imaged is formed by both the objective and eyepiece. A weak lens is used for the objective and a strong lens is normally used for the eye piece lens. P7.6 Ray diagrams
  • 37. Key concepts P7.6 a Look at the photograph and information and answer all the questions: Ray diagrams for a reflecting telescope The parabolic mirror used in a reflecting telescope has many advantages over the glass lens, it can be made much larger so that it can gather more light and therefore produce better images of dim stars. It is also is much easier to produce a large mirror with no imperfections than a large lens. Lenses cannot be made larger than one metre in diameter or the shape would distort under its own weight. Give two uses for a curved parabolic mirror like the one found in reflecting telescopes ? When using a large diameter radio telescopes that use parabolic mirror explain why the detector that collects the parallel rays needs to be mobile ? object image
  • 38. Key concepts P7.6 b Look at the photograph and information and answer all the questions: Explain why the lenses need to be able to move in a reflecting telescope ? Which type of telescope is used to image the very distant corners of the Universe ? Ray diagrams for a refracting telescope A refracting telescope works by having two converging lenses of different powers set in line with each other. The lenses can be moved towards or away from each other to focus the image. The smaller lens is called the eyepiece and the larger lens is called the objective lens. The light gathering power of the telescope is given by D which is the diameter of the lens. principal axis object image Lenses can be moved
  • 39. Key concepts P7.6 b Look at the photograph and information and answer all the questions: Look at the above diagram and explain why the image formed is upside down or inverted ? Our eyes also use a converging lens to form an image on the retina’s surface. Explain why we do not see an inverted image ? Ray diagrams for a refracting telescope Explaining why the image of a galaxy is both smaller and upside down when using a refracting telescope is simple. If you look at the above ray diagram you can see that the objective lens gathers light form two sides of the galaxy (blue and yellow) and that when the image travels through the lens it becomes inverted and smaller. lens Distant galaxy image
  • 40. P7.6 Plenary Lesson summary: distant star weak focused Friday 21 October 2011 All refracting telescopes use the same principles. The combination of an objective lens and some type of eyepiece is used to gather more light than the human eye could collect on its own, focus it, and present the viewer with a brighter, clearer, and magnified virtual image. How Science Works: Research into how our own atmosphere affects how we view the Milky Way and beyond form the Earth surface. Look into how night light pollution can also affect star gazing in big cities. Preparing for the next lesson: From distant _____ or galaxies, parallel lights rays enter the objective lens. The parallel rays are _________ by the objective lens, so a real image is formed. The objective lens is usually ______ to form a large image. The eyepiece lens magnifies the image so you can see the _______ object Decide whether the following statements are true or false : False True 3: The image formed by a refracting telescope is always inverted ? False True 2: Light rays from distant galaxies travel in parallel lines ? False True 1: The focal length of a converging lens is measured in metres ?
  • 41. P7.7 Images of stars Decide whether the following statements are true or false:
    • Lesson objectives:
    • Understand the effects of the atmosphere on light from stars
    • Understand the need to reduce light pollution in order to view the night sky
    • Understand how digital image processing can improve images of stars
    We will focus on. Friday 21 October 2011 First activity: People often say that you have to wait about 10 minutes before you can see all the stars in the night sky, explain why ? Literacy: Atmosphere, orbit, telescopes, image , reflection, refraction, absorption, refraction, scintillation, light pollution, digital image processing Numeracy: To reduce light pollution city authorities in Rome, Italy every night switch off 170,000 of the cities street lights, in an effort to reduce light pollution by 40%. In the UK councils are also thinking of doing the same thing. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
  • 42. Extension questions: 1: What types of radiation does the Earth’s atmosphere absorb ? 2: What types of radiation passes through the Earth’s atmosphere ? 3: Why can the Hubble space telescope capture better images than a telescope on the Earth’s surface? 4: Look up at the nigh sky in London or any major city, why do you only see a very few stars of within the Milky Way ? 5: Explain why stars ‘twinkle’ when viewed from Earth ? Know this: a: Know how the atmosphere can affect the light emitted from stars and other distant objects. b: Know the effect of light pollution on viewing stars from Earth’s surface. Friday 21 October 2011 Introduction: In order to capture the best images of stars a telescope can be sent into orbit around the earth above the earths atmosphere. This is an advantage because the atmosphere absorbs and refracts some of the radiation given out by the stars, placing a telescope outside the atmosphere ensures that all of the radiation emitted reaches the telescope therfore giving a much clearer image. Stars appear to ‘twinkle’ in the night sky due to an effect called scintillation. As a ray of light from a star passes through the atmonsphere is is refracted in different directions by areas of the atmosphere that area different densities, this refraction of the light causes the ‘twinkling’ of the stars even though the light they emit is constant. P7.7 Images of stars
  • 43. Key concepts P7.7 a Look at the photograph and information and answer all the questions: Look at the map of Europe, showing levels of light pollution, which European countries are responsible for the highest levels of light pollution ? Explain why telescope place it geostationary orbit above the Earth’s surface are not affected by light pollution ? The ‘Campaign for Dark Skies’ is a campaign aimed at reducing light pollution from cities. Light pollution makes it difficult for astronomers to clearly view stars as the light from cities reflects up into the lower atmosphere where it is scattered and enters any nearby telescope, reducing the quality of the image and obscuring many stars in the Milky Way much like the Sun does during daytime. Look at Light pollution in the UK, explain why you may have to ravel to Africa away form the coast to see the true beauty of the Milky Way ? Light pollution
  • 44. Look at the photograph and information and answer all the questions: Look up at the night sky and you are looking through a very small part of our own galaxy. Although light pollution in cities hinders our view, in unpopulated countryside the Milky Way is awesome. Viewed at night you can see why it is named the Milky Way. A milky light crosses the sky, full of stars, all many hundreds of light years away. Our own galaxy stretches 100,000 light years across. Explain why large telescopes are built on high mountains far away from large cities...think of two reasons ? Explain why we only see a few stars that belong to the Milky Way from large cities like London ? Explain why NASA has spent billions of dollars putting the Hubble telescope high above our atmosphere in space ? Key concepts P7.7 b
  • 45. Key concepts P7.7 c Look at the photograph and information and answer all the questions: Look at the map of the UK showing levels of light pollution, which UK cities or counties are responsible for the highest levels of light pollution ? Look at the World map, where would you build an observatory away form light pollution? Light pollution obscures the stars in the night sky for city dwellers. Light pollution is a side effect of industrial civilization. Its sources includes lighting, advertising, offices, factories, streetlights, and illuminated sporting venues. It is most severe in highly industrialized, densely populated areas of North America, Europe, and Japan and in major cities in the Middle East and North Africa. Light pollution across the planet UK at night
  • 46. P7.7 Plenary Lesson summary: colour refracting layering atmosphere Friday 21 October 2011 Light pollution is a broad term that refers to multiple problems, all of which are caused by inefficient, unappealing, or (arguably) unnecessary use of artificial light. Specific categories of light pollution include light trespass, over-illumination, glare, light clutter, and skyglow. A single offending light source often falls into more than one of these categories. How Science Works: Research into what we can see by using our own eyesight, for example the star constellations, the phases of the moon and sunset and sunrise. Preparing for the next lesson: Space telescopes capture better images because they are above the earth’s __________, avoiding the effects of the atmosphere absorbing or ________radiation. Digital image processing can improve the quality of images captured by adding effects such as false ________ or removing background ‘noise’ by ________ images. Decide whether the following statements are true or false : False True 3: Land telescopes produce better images than space telescopes ? False True 2: In remote areas telescopes are often placed to avid light pollution ? False True 1: In London you can see the Milky Way in all its glory ?