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Light
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What type of a wave is light?
Light is a little odd, but if anything it is a Transverse Wave If light is a wave, then what is waving? It is a fluctuating electric and magnetic field and is often called Electromagnetic Radiation
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The Electromagnetic Wave
All waves require a medium to travel through!!!! β¦.. Except Light!?!? It moves through space propagating itself
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How fast is light? The speed of light represents the Universe's speed limit All types of light travel at the same speed 3*108 m/s In a vacuum
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Practice = 53418.8 m π£=π/π‘ π‘=π/π£ π‘=53418.8/(3β 10 8 ) π‘=1.78β 10 β4 π
The distance between the State Capitol and Westlake High school is 33.2 miles. How long would a flash of light take to get from one to the other? 33.2 mi 1609 m = m 1 mi π£=π/π‘ π‘=π/π£ π‘= /(3β 10 8 ) π‘=1.78β 10 β4 π If the distance between the Earth and the Sun is 1.49*10^11 m, how long does it take light to move between the two? π‘=496.7π or 8.28 min π‘=π/π£ π‘=(1.49β )/(3β 10 8 )
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The Electromagnetic Spectrum
There is much more to light than what the eye can see! π£=πβπ π=πβπ The speed of light is a constant!
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Does Light carry Energy?
Yes!!!! Sunlight is warm β¦ You can power things with photovoltaic cells β¦ Plants get energy through photosynthesis So how do you measure the energy light carries? -It all travels at the same speed -It has no mass For most waves, you measure the energy they carry by looking at the amplitude. Light breaks the rules again!!! ?
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The Photoelectric Effect
Through this experiment we realize that the energy light carries is not proportional to its amplitude, but rather to its frequency!
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βhβ is Plankβs Constant
Light and Energy From the Photoelectric Effect we learn: Increase Amplitude = More Electrons Increase Frequency = Higher Energy Electrons πΈ=βπ βhβ is Plankβs Constant = 6.63 * 10-34 Low Energy High Energy
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Practice π= 3β 10 8 (460β 10 β9 ) π=πβπ 3β 10 8 =(460β 10 β9 )βπ
*10^-9 How much energy does Blue light (Ξ» = 460nm) have? π= 3β (460β 10 β9 ) π=πβπ 3β 10 8 =(460β 10 β9 )βπ π=6.52β hz πΈ=ββπ πΈ=(6.63β 10 β34 )β(6.52β ) πΈ=4.32β 10 β19 π½
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Does Light experience a Doppler Shift?
YES!!!!!!!! BLUE SHIFT RED SHIFT
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Galaxy velocities
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