7PTYS_206_light_heat_from_planets_stars

7PTYS_206_light_heat_from_planets_stars - PYTS/ASTR 206...

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PYTS/ASTR 206 – Light and Heat from Planets and Stars 1 Announcements Homework due this Thursday. Everyone should have (at least) looked at it by now.
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PTYS/ASTR 206 – The Golden Age of Planetary Exploration Shane Byrne – [email protected] Light and Heat from Planets and Stars
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PYTS/ASTR 206 – Light and Heat from Planets and Stars 3 What is radiation? Blackbody radiation Temperature and radiation Emissivity Sunlight and starlight Energy for planetary surfaces Reflection Albedo and color Scattering Emission and absorption lines Atomic structure Emission and absorption spectra The Doppler effect In this lecture…
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PYTS/ASTR 206 – Light and Heat from Planets and Stars 4 Visible light is electromagnetic radiation Not the same as radioactivity Mostly sub-atomic particles What’s radiation?
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PYTS/ASTR 206 – Light and Heat from Planets and Stars 5 Changing electric field produces the magnetic field And vice-versa These fields vary in one place – but the disturbance travels Waves described by: Wavelength Frequency (waves passing by per sec.) Speed Amplitude These are related: Speed = wavelength * frequency E.g. for blue light Wavelength ~ 3*10 -7 m Speed ~ 3*10 8 m/s How many wave per sec? Freq. = speed/wavelength Freq. = 10 15 Hz 1,000,000,000,000,000 waves per second!
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PYTS/ASTR 206 – Light and Heat from Planets and Stars 6 Radiation (light) travels fast Faster than anything else in the universe… but not infinitely fast. Exactly 299,792,458 m/s (called ‘c’) in a vacuum It’s exact because it defines what a meter is Slower when going through material Romer studied the timing of Jupiter eclipsing its moons Observations in 1676 Made possible with telescopes Io enters Jupiter’s shadow earlier or later than expected.
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PYTS/ASTR 206 – Light and Heat from Planets and Stars 7 These are all the same phenomena The wavelength determines – what we call it & how energetic it is
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PYTS/ASTR 206 – Light and Heat from Planets and Stars 8 White light is a mix of different wavelengths (colors) Three types of cone cell in eyeball Each detects different wavelengths Not too sensitive Only one kind of rod cell Very sensitive – used for night vision Only one kind so no color vision at night These cells don’t detect other wavelengths
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9 Both – depends on the situation Diffraction – light bends around corners – like a continuous wave Interference – light adds together and cancels out – like a continuous wave Photoelectric effect - Einstein Light travels in discrete packages Called photons Photon energy depends on frequency A single photon removes an electron from a metal …if its energy is high enough… The number of photons doesn’t matter Waves or particles?
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This note was uploaded on 01/01/2011 for the course PTYS/ASTR 206 taught by Professor Shanebyrne during the Spring '07 term at Arizona.

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7PTYS_206_light_heat_from_planets_stars - PYTS/ASTR 206...

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