• Support PF! Buy your school textbooks, materials and every day products Here!

Effect of frequency & Intensity on number of photons

  • Thread starter Nancee
  • Start date
1
0
1. Homework Statement
Electromagnetic radiation of wavelength λ and Intensity I, when incident on a metal surface, causes n electrons to be ejected per unit time. The maximum kinetic energy of the electrons is Emax.

State and explain the effect, if any on n and Emax when the wavelength λ is reduced but the intensity I is unchanged.

2. Homework Equations
E=hf, and I'm not sure what else

3. The Attempt at a Solution
I solved this question with 2 different teachers, the first said that n will not change as I is unchanged. The other said that n will reduce because:
number of photons=Intensity/energy of 1 photon
I trust both teachers so I'm really confused now.
 

Answers and Replies

Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,598
6
The other said that n will reduce because:
number of photons=Intensity/energy of 1 photon
I think that one of your teacher's misread the question because this is faulty logic. The question explicitly states that the intensity remains constant.
 
kdv
336
1
I think that one of your teacher's misread the question because this is faulty logic. The question explicitly states that the intensity remains constant.
I happen to agree with that teacher and disagree with the first one!!


yes, the intensity stays the same. But if you decrease lambda, you increase the energy of each photon.
Therefore, in order to get the same intensity there must be fewer photons present. Therefore fewer electrons will be ejected.
 
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,598
6
I happen to agree with that teacher and disagree with the first one!!


yes, the intensity stays the same. But if you decrease lambda, you increase the energy of each photon.
Therefore, in order to get the same intensity there must be fewer photons present. Therefore fewer electrons will be ejected.
You are of course correct, scratch what I said. I apologise for any confusion. Perhaps it's time for a rest... :redface:
 

Related Threads for: Effect of frequency & Intensity on number of photons

  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
3
Views
3K
Replies
3
Views
4K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
0
Views
3K
Replies
5
Views
2K
  • Last Post
Replies
4
Views
10K
  • Last Post
Replies
4
Views
560
Top