A. Electromagnetic Waves 1. Light from the past a. Light seen from stars, may have left that star many years ago. b. Light and other energy leaving a star are forms of radiation. c. Radiation is energy that’s transmitted from one place to another by electromagnetic waves. d. Because of this radiation, its called electromagnetic radiation
B. Electromagnetic Radiation 1. Sound waves, a type of mechanical waves can’t travel through empty space. a. Then how do we hear the voices of astronauts while they are in space? b. When they speak into a microphone, the sound is converted into electromagnetic waves called radio waves. c. They are then converted back into sound by electronic equipment and audio speakers.
2. Types of electromagnetic radiation a. Radio waves, visible light, gamma rays, X- rays, ultraviolet waves, infrared waves, and microwaves.3. Measured in wavelength and frequency. a. Wavelength is the distance from the top of one wave to the next. b. Frequency is the number of wavelengths that pass by a certain point in one second. c. As wavelength increases; frequency decreases and vice versa.
C. Speed of Light 1. Light is part electricity and part magnetism 2. Speed of light is 3.8 X 108 m/s or 300,000 km/s 3. All electromagnetic waves travel at the speed of light. 4. Universe is so large it takes millions of years from the light from some stars to reach the Earth. 5. Once electromagnetic radiation from stars and other objects reach Earth, we can use it to learn about the source of the electromagnetic radiation.
6. One tool used for observing electromagnetic radiation from distant sources is a TELESCOPE.
D. How we use Electromagnetic Waves 1. Light from the Past a. Stars are images from the past. b. Light from stars takes time to travel through space. c. Our Sun is about 150 million kilometers away (about 8 minutes travel time) d. Alpha Centauri (our closest neighboring star) is about 40 Trillion Kilometers away; about 4.2 years travel time. e. Light travels at 300,000 km/sec or 186,000 miles/second. f. Light travels 9.5 trillion kilometers in a year (this is one light year). g. A light year measures both distance and time!!!
E. Radio Waves 1. Longest wavelength: 105 to 10-1 meters. 2. Lowest frequency: 103 to 109 Hertz 3. Used for communication and information transfer.
F. Microwaves 1. Wavelength: 10 -1 to 10 -3 meters & Frequency: 109 to 1011 Hertz. 2. Used for communication, Information transfer and cooking.
G. Infrared 1. Wavelength: 10 -3 to 10 -6 meters & Frequency: 1011 to 1014 Hertz 2. Used for heat production and Thermography. 3. “Seen” by some insects and animals.
H. Visible Light 1. Wavelength: 10 -7 meters & Frequency: 1015 Hertz 2. Colors seen by human eyes
I. Ultraviolet 1. Wavelength: 10 -7 to 10 -9 meters & Frequency: 1015 to 1017 Hertz 2. “Seen” by some insects 3. Cause of tanning, sunburn, skin cancer 4. Degrades rubber & plastic materials (fades cloth & paper)
J. X-Rays 1. Wavelength: 10 -9 to 10 -11 meters & Frequency: 1017 to 1019 Hertz 2. Bone scans, Information transfer
K. Gamma Rays 1. High level radiation (Very Dangerous) 2. Shortest wavelength: 10 -11 to 10 -15 Meters 3. Highest frequency : 1019 to 1023 Hertz
L. How We Use Telescopes 1. We use the electromagnetic spectrum to observe space. 2. Optical Telescopes a. Produce magnified images of objects. b. Visible light is collected by mirrors or lenses and then focused. 3. There are two types of telescopes. a. Optical Telescopes (You need light for these) b. Radio Telescopes.
M.Refracting Telescope (Optical) 1. Light from an object passes through a convex objective lens and is bent to from an image on the focal point. 2. The images is then magnified by the eyepiece. 3. Limited in size 4. Worlds refracting mirror is Yerkes Refracting Telescope a. Just over a meter in diameter (distance across)
Diagram of a Refracting Telescope FocalConvex Lens Point Eyepiece
N.Reflecting telescopes 1. Light passes trough the telescope housing to a concave mirror 2. Mirror reflects light to a flat mirror 3. Flat mirror redirects light to a focal point 4. Light passes through the focal point, to the eyepiece 5. Eyepiece magnifies image 6. Largest in the world = 10 meters wide
O. Optical Telescope Uses: 1. Most “home” use telescopes are optical. 2. Used to see moon features and close planets. 3. Scientific optical telescopes are housed in OBSERVATORIES. a. Observatories have domed shape roofs that open. b. Observatories built on mountains or deserts, far away from cities. 1. Prevents city light interference and pollution blurring. 2. Decreases “down time” due to poor weather. c. Not all telescopes are housed in observatories.
P. Radio Telescopes. 1. Designed to pick up radio waves emitted from space. 2. Usable in any weather!!! a. Radio waves are concentrated by dish shaped body. b. Concentrated waves are directed to a focal point. c. Focal point is fixed with a receiver. d. Receiver transmits information to a computer.
3. Uses of a Radio Telescope a. Detects objects deep in space. b. Maps the Universe. c. Searches for intelligent life in space.4. Largest Radio Telescope in the world is 300 meters wide.
Q. Hubble Telescope (Reflecting Telescope) 1. Launched in 1990 by the space shuttle Discovery. 2. Since Hubble did not have to view space through the Earth’s atmosphere, it should have produced very clear images. 3. However there was a mistake in the largest mirror used in the Hubble Telescope!!!! 4. Images were not as clear as expected. 5. December 1993 first set of repairs were fixed by astronauts. 6. Has been repaired numerous times since. a. Hubble Telescope Link/