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10 Cards in this Set
- Front
- Back
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ways energy can be transmitted
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moving matter, moving particles, or by waves
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properties of waves
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rectilinear propagation- means that light travels in a straight line EX: if you have a candle and put pieces of paper with a small hole cut out in a line you can see the light but if you move one of the papers you no longer see it
reflection- light hits a surface and bounces off EX: mirror refraction- light can bend when it under goes a change of speed or medium through which it is traveling EX: where a fish looks in water is not where it actually is interference- when two or more light waves combine to either reinforce of cancel each other EX: this is why soap bubbles show the colors of the rainbows diffraction- the movement of light waves around an object EX: when a cloud is in front of the sun you can still see the rays going around it |
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Things known about light as they are found out
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people in the time of Plato knew light reflected
the refraction of light was observed by the greeks in the second century AD Alhazen proved that visual rays did not come from the eye People in the seventeenth century knew about the propagation, reflection, and refraction of light the idea that light is particles is called the Corpuscular theory the main advocate of this theory was Newton the main advocate of the wave theory was Huygens, supported by Robert Hooke there would be a conflict of these two idea for over a century |
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Newton believed light
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consisted of streams of particles called corpuscles
rectilinear propagation- newton said it made more sense for light to be particles because sound bends around a corner but you cannot see light behind an obstacle reflection- light bounces off a smooth surface as a ball would refraction- Newton constructed a model to show how a ball refracts under a change of speed, but his theory depended on light moving faster in denser materials than in less dense materials Newton proved the three properties of light as particles, but the people back then did not know of interference or diffraction |
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Huygens is considered
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to be the founder of the wave theory
rectilinear propagation- Huygens’ principle which says that each point on a wave front may be regarded as a new source of disturbance reflection- light bounces off a surface like a sound wave does refraction- Huygens said that light would need to move faster in less dense materials than in more dense materials |
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the fall of newton's theory
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In the early 1800s the interference and diffraction of light were discovered
these properties of light supported the wave theory and the corpuscular theory was largely abandoned then it was discovered that light moves faster in less dense materials than in dense materials, so Newton’s theory lost even more followers |
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electromagnetic theory
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Maxwell thought that heat, light, and electricity are all transmitted at the speed of light as electromagnetic waves
He also thought that each electromagnetic wave was divided into two parts an electric field and a magnetic field He found that an electromagnetic wave is two waves transversed with these two parts at right angles Hertz then came along and proved that maxwell was correct in this theory |
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electromagnetic spectrum
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(in frequencies low to high)
power frequencies- used in electric generators radio waves- used for radio stations infrared radiation- used for heating visible spectrum- the colors we see ultraviolet radiation- give us sunburn and suntans X rays- used to x-ray the body gamma rays- used to destroy certain types of cancer cosmic rays |
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the photoelectric effect
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defied explanation based on the electromagnetic wave theory of light
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light
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radiant energy to which the human eye is sensitive
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