# Maximum velocity of electrons?

1. May 9, 2010

### eq123

i've been trying to figure out this problem..

The longest wavelength of light that causes electrons to be ejected from the surface of a copper plate is 243 nm. What is the maximum velocity of the electrons ejected when light of wavelength 200. nm shines on a copper plate?

the answer is 6.22 × 105 m/s

any ideas?

2. May 10, 2010

### espen180

Ek=hf-φ

Where φ is the work function, the lowest energy that must be supplied to tear off an electron, and hf>φ.

3. May 10, 2010

### alxm

Read the forum rules!
This isn't the correct board for homework problems. And you should show some attempt to having solved the problem.

4. May 10, 2010

### eq123

thank you.. but how can i relate this to the wavelength concept?
this is not a homework problem.. it is an old exam question..

i would appreciate any additional information..

5. May 10, 2010

### PhaseShifter

$$f={c\over\lambda}$$