# Homework Help: Threshold frequency in light

1. May 13, 2006

### mmg0789

the question is:

in a photoelectric effect, it is found that incident photons with energy 5.00 eV will produce electrons with a maximum kinetic energy 3.00 eV. What is the threshold frequency of this material?

the equation i have to work with is KE=hf-hf(sub t) and here the way to figure out threshold freq is to solve for f(sub t) with would equal
hf-KE/h

and KE would be found--i guess--by multiplying (3)(1.6e10^-19)

i did al that but i dont know what the 5.00 eV is and what the frequency is

Last edited: May 13, 2006
2. May 13, 2006

### Astronuc

Staff Emeritus
What is the significance of the difference in energy between the incident photon and the maximum kinetic energy of the photoelectron?

What is the relationship between photon energy and frequency?

3. May 13, 2006

### mmg0789

huh!? i hav no idea-

4. May 13, 2006

### Astronuc

Staff Emeritus
When a photon is absorb by an electron, part of the energy goes to releasing the electron from its bound state, and the excess energy goes into the kinetic energy of the now photoelectron.

The energy of a photon, E is proportional to frequency of the photon. Hint - Planck's constant.