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### Post module quiz #25

Posted: Fri Apr 13, 2018 5:05 pm
25. Photoelectric experiments gave rise to a new equation relating the energy of light to its frequency. Select the right equation.

A. λv = c

B. Ek = mv2/2

C. mv2/2 = hv - φ

D. E = hv

E. None of the above

I thought the answer would be c, but it said this was wrong. Can someone please explain?

### Re: Post module quiz #25

Posted: Fri Apr 13, 2018 5:52 pm
Would it be A because c= the speed of light?

### Re: Post module quiz #25

Posted: Fri Apr 13, 2018 9:52 pm
I believe it would be option A because the photoelectric experiment showed that the wavelength of light is equal to the ratio of the speed of light to the frequency.

### Re: Post module quiz #25

Posted: Sat Apr 14, 2018 12:38 am
Option A contains v (frequency of light), but c is the speed of light, not the energy of light.
Option B has to do with kinetic energy.
Option C is the equation we used in class, relating the energy of an incoming photon to the threshold energy needed to eject an electron and the resulting kinetic energy of the electron. Although this equation does include v (frequency of light) and it does have to do with energy, it has to do with threshold energy and kinetic energy of an electron, not the energy of the light source itself.
Option D: E = hv directly relates E (amount of energy per photon) to v (frequency of light) so I think the answer is D.

### Re: Post module quiz #25

Posted: Sat Apr 14, 2018 9:23 am
I also think the answer is D, because it directly relates energy E to frequency $\nu$.

### Re: Post module quiz #25

Posted: Sun Apr 15, 2018 12:33 pm
I think the answer would be choice D. The equation E= hv is the best answer because it creates a direct correlation between energy and the frequency.

### Re: Post module quiz #25

Posted: Sun Apr 15, 2018 7:54 pm
The best answer is D because it showed quantization of energy for the photon.