7. Why did the introduction of the photon effectively end classical physics? How

Question

7. Why did the introduction of the photon effectively end classical physics? How did Einstein's explanation of the photon contradict the classical explanation of light? 8. 9. Provide an example of an experiment that Einstein's theory could not explain. Using the concept of quantum and photons, explain the difference between a 100 W and a 40 W light bulb if they both produce only green light. Answer the following questions in your explanation: 10. a. Why does the 100 W bulb appear brighter than a 40 W bulb? b. Why would you expect the 100 W bulb to feel hotter than the 40 W bulb? ADLC Physics 30

Explanation / Answer

7.

It was the first "particle" observed to have both the properties of a true particle, and the properties of waves. Thomas Young's double-slit experiment proved that photons behave like electromagnetic waves when unobserved, and like particles while under observation.

8.

When light shines on the surface of a metallic substance, electrons in the metal absorb the energy of the light and they can escape from the metal's surface. This is called the photoelectric effect.  Using the idea that light is a wave with the energy distributed evenly throughout the wave, classical physicists expected that when using very dim light, it would take some time for enough light energy to build up to eject an electron from a metallic surface.

But experiments show that if light of a certain frequency can eject electrons from a metal, it makes no difference how dim the light is. There is never a time delay.

Albert Einstein said that Each clump of light energy is called a photon and each photon has an energy equal to hf (Planck's constant times the frequency of the light). Therefore the energy of light is not evenly distributed along the wave, but is concentrated in the photons.

9.

Young's Double Slit Experiment.

10.

100 W will have more no. of photons than the 40 W bulb

(a)

Due to more power dissipation. P=(V*V)/R

(b)

Beacuse of more power disipation more heat will be generated.

H = P*time

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