Light present

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Light present

  1. 1. LIGHT What is light and why is it essential to life? QuickTime™ and a QuickTime™ and a TIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. QuickTime™ and a QuickTime™ and a TIFF (Uncompressed) decompressorTIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
  2. 2. What is light ? Light is a form of energy. It can be changed from one form of energy to another.  For example, light entering your eye is changed to chemical and electrical energy which is transmitted to your brain. Light energy can only be produced from other forms of energy. QuickTime™ and a QuickTime™ and a QuickTime™ and aTIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. are needed to see this picture.
  3. 3. Two types of light energyObjects thatconvert theirenergy to producetheir own light are QuickTime™ and asaid to be TIFF (Uncompressed) decompressor are needed to see this picture.LUMINOUS.LUMINOUSFor example, some fishliving in the depths of theocean produce their ownlight to attract prey.
  4. 4. Two types of light energyNON LUMINOUS objects do not give off their own light, they reflect light. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.For example you can see a car because it is reflecting light from the sun.
  5. 5. But how does light travel? - Ocean waves travel on the surface of the water. You can QuickTime™ and aTIFF (Uncompressed) decompressor are needed to see this picture. see them and you can feel them. - Have you ever seen a flag on a windy day? The wind creates waves in the flag. - Sound is also a type of wave that we cannot see. - Sound waves need something to travel through (like waves through the ocean or wind through a flag). Sound can travel through air because air is made of molecules. These molecules carry the sound waves by bumping into each other, like dominoes knocking each other over. Sound can travel through anything made of molecules - even water! - There is no sound in space because there are no molecules there to transmit the sound waves.
  6. 6. All light has both particle-likeand wave-like properties.Light is made of discrete QuickTime™ and a TIFF (Uncompressed) decompressorpackets of energy called are needed to see this picture.photons.Photons travel at the speed oflight (300,000 km/s).
  7. 7. So light is a form of energy? • White light is all colours, like the colours of the rainbow. • Sir Isaac Newton discovered the colour of light by shining white light through a prism. • This is called the "visible light spectrum." QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
  8. 8. Light is energy - Light is energy and there is energy beyondvisible light. - The visible light spectrum is a part of a largerspectrum called the: Electromagnetic Spectrum. Spectrum
  9. 9. ELECTROMAGNETIC ENERGY When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven, you are using electromagnetic energy. You depend on this energy every hour of every day. Without it, the world you know could not exist. Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an x-ray machine uses yet another portion. QuickTime™ and a QuickTime™ and a QuickTime™ and aTIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. are needed to see this picture.
  10. 10. OUR PROTECTIVE ATMOSPHERE Our Sun is a source of energy across the full spectrum, and its electromagnetic radiation bombards our atmosphere constantly. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. However, the Earths atmosphere protects us from exposure to a range of higher energy waves that can be harmful to life.Exposure to Gamma rays, x-rays, and someultraviolet waves waves can alter atoms andmolecules and cause damage to cells in organic QuickTime™ and a TIFF (Uncompressed) decompressormatter. are needed to see this picture.These changes to cells can sometimes be helpful,as when radiation is used to kill cancer cells, andother times not, as when we get sunburned.
  11. 11. Beams of Light Electromagnetic waves do not need molecules to travel, unlike sound waves. Electromagnetic waves can travel through air and solid materials as well as empty space. Light is an electromagnetic wave we can see. This is why astronauts on spacewalks use radios to communicate. Radio waves are one kind of electromagnetic wave.
  12. 12. Rays of Light & reflections A stream of light rays is called a ray of light. Light can pass through some materials and it can also be reflected by other materials.TRANSPARENT TRANSLUCENT OPAQUE OBJECT OBJECT OBJECTGlass, clear water,clear plastic cling Frosted glass or Wood, cement, wrap. stained glass concrete windows.
  13. 13. What is a shadow? A shadow outlines the area where light cannot reach. There are two types of shadows.UMBRA SHADOW PENUMBRA SHADOWThis is a This is a semi shadowcomplete shadow. with usually a fuzzyThink of using a torch outline.to make animalshadows on a wall.
  14. 14. WAVESTOWN This Doppler-radar image seen on TV weather news uses microwaves for local QuickTime™ and a QuickTime™ and a weather forecasting. TIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Gamma Rays!! QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and ae™ and a TIFF (Uncompressed) decompressor Infra-red decompressorhis picture. Thermal are needed to see this picture. Imaging
  15. 15. Reflections & Plane Mirrors One property of light is that it reflects off surfaces. When you look at yourself in a plane mirror you see an image of yourself. The reflection in the mirror appears to originate from inside the mirror at a distance equal to the distance the person is in front of the mirror. Plane mirrors produce virtual, upright images that are the same size as the object and the same distance from the surface of the mirror.
  16. 16. The law of reflection When a ray of light strikes a plane mirror, the light ray reflects off the mirror. Reflection involves a change in direction of the light ray.

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