# Some Photoelectric Questions

#### Procrastinate

1. Is binding energy equivalent to work (W)?

2. A He-Ne gas laser produces monochromatic red ligth with a wavelength of 6.3 x 10-7. If the beam is reflected normally from a mirror, what is the change in momentum of each photon on reflection?

I am particularly confused about this question. I used delta p = m(v - u) where v was the speed of light but it didn't result in the correct answer. Could anyone please give me a hint?

I also couldn't figure out what the mass of a photon was so I used the mass of an electron which I am sure is wrong.

#### ZapperZ

Staff Emeritus
2018 Award
1. Is binding energy equivalent to work (W)?
Is this work, or "work function"?

2. A He-Ne gas laser produces monochromatic red ligth with a wavelength of 6.3 x 10-7. If the beam is reflected normally from a mirror, what is the change in momentum of each photon on reflection?

I am particularly confused about this question. I used delta p = m(v - u) where v was the speed of light but it didn't result in the correct answer. Could anyone please give me a hint?

I also couldn't figure out what the mass of a photon was so I used the mass of an electron which I am sure is wrong.
You need to go back and find out the expression for the momentum of light. Hint: it is NOT p=mv!

Zz.

#### Procrastinate

Is this work, or "work function"?

Work function: E = W + KE

You need to go back and find out the expression for the momentum of light. Hint: it is NOT p=mv!

Zz.
1. I supposed binding energy many the threshold energy that was required to illuminate light.

2. Is it de Broglie's wavelength?: p = c/lambda

I didn't think it was this because the change in momentum is a different formula.

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