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Light.

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Presentation on theme: "Light."β€” Presentation transcript:

1 Light

2 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

3 The Electromagnetic Wave
All waves require a medium to travel through!!!! ….. Except Light!?!? It moves through space propagating itself

4 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

5 Practice = 53418.8 m 𝑣=𝑑/𝑑 𝑑=𝑑/𝑣 𝑑=53418.8/(3βˆ— 10 8 ) 𝑑=1.78βˆ— 10 βˆ’4 𝑠
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 𝑣=𝑑/𝑑 𝑑=𝑑/𝑣 𝑑= /(3βˆ— 10 8 ) 𝑑=1.78βˆ— 10 βˆ’4 𝑠 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? 𝑑=496.7𝑠 or 8.28 min 𝑑=𝑑/𝑣 𝑑=(1.49βˆ— )/(3βˆ— 10 8 )

6 The Electromagnetic Spectrum
There is much more to light than what the eye can see! 𝑣=πœ†βˆ—π‘“ 𝑐=πœ†βˆ—π‘“ The speed of light is a constant!

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8 Does Light carry Energy?
Yes!!!! Sunlight is warm … You can power things with photovoltaic cells … 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!!! ?

9 The Photoelectric Effect
Through this experiment we realize that the energy light carries is not proportional to its amplitude, but rather to its frequency!

10 β€œh” is Plank’s Constant
Light and Energy From the Photoelectric Effect we learn: Increase Amplitude = More Electrons Increase Frequency = Higher Energy Electrons 𝐸=β„Žπ‘“ β€œh” is Plank’s Constant = 6.63 * 10-34 Low Energy High Energy

11 Practice 𝑓= 3βˆ— 10 8 (460βˆ— 10 βˆ’9 ) 𝑐=πœ†βˆ—π‘“ 3βˆ— 10 8 =(460βˆ— 10 βˆ’9 )βˆ—π‘“
*10^-9 How much energy does Blue light (Ξ» = 460nm) have? 𝑓= 3βˆ— (460βˆ— 10 βˆ’9 ) 𝑐=πœ†βˆ—π‘“ 3βˆ— 10 8 =(460βˆ— 10 βˆ’9 )βˆ—π‘“ 𝑓=6.52βˆ— hz 𝐸=β„Žβˆ—π‘“ 𝐸=(6.63βˆ— 10 βˆ’34 )βˆ—(6.52βˆ— ) 𝐸=4.32βˆ— 10 βˆ’19 𝐽

12 Does Light experience a Doppler Shift?
YES!!!!!!!! BLUE SHIFT RED SHIFT

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14 Galaxy velocities

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