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24 Cards in this Set
- Front
- Back
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What is light?
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Light is electromagnetic radiation,
not all light is visible, Color->wavelength Frequency-> |
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What can we by knowing the 'physics of light'
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Temperature, distance, chemical composition
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History of Light
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Empirical laws for light well developed by the time of Newton, but the 'nature' of light still was a mystery
Newton proposed that light was a "particle" He correctly noted that "white light" was a combination of other colors by use of a prism |
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What did Newton propose light was?
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A "particle"
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Did Newton think that light was a wave?
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He rejected the idea that light was 'wave', though he ended up being wrong (but not compeletly)
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Huygens and Light
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●Huygens proposed that light was a “wave”
●Interference experiments by Young (early 1800's) conclusively demonstrated the wave character of light |
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Characteristic of Waves
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wavelength- for light this determines color
frequency- for light this determines energy Amplitude- this determines total energy |
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Wavelength
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For light this determines color. Peak to peak distance
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Frequency
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For light this determines energy. Oscillations per second
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Amplitude
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this determines "total energy". maximum displacement from equilibrium
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Electromagnetic Spectrum
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The speed of light (in vacuum) is determined by the product of wavelength and frequency. "Longer" wavelengths are said to be 'redder'. "Shorter" wavelengths are said to be 'bluer'. All light travels the same speed in a vacuum. Not all light is visible.
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Shorter Wavelengths
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'bluer'
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Longer wavelengths
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'redder'
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Is all light visible?
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No, not all light is visible.
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Does all light travel the same speed in a vacuum?
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yes all light travels the same speed in a vacuum
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Wavelengths/frequency
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The energy is proportional to the frequency. Longer wavelength-> low energy. Shorter wavelength->higher energy (X-ray, UV, Gamma-rays). All light travels the same speed. Our eyes are only sensible to that light in the narrow range from about 450 nm to 700nm. Infared-> far red. Ultraviolet->extreme violet
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Longer wavelength
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Low energy
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Shorter Wavelength
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higher energy
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Infrared
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far red
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Ultraviolet
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extreme violet
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Doppler Effect
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Relative motion between observer and source causes an observed change in frequency and/or wavelength. Phenomena is common to all waves. But for light is subtly different and for sound. Motion toward/motion away
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Motion toward
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blue shift, higher frequency, shorter wavelength
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motion away
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red shit, lower frequency, longer wavelength
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Light as a particle.
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Newton wasn't completely wrong. A compete understanding of light requires and interpretation based on both "wave" and "particle" phenomena. A particle of light is called a 'photon'. Each photon carries a specific amount of energy that is
proportion to the frequency E=hf ● 'h' is Planck's constant ●The particle nature of light is most important when it interacts with matter. |
