# De Broglie and other Quantum Questions

Hi, just some quantum physics questions. I've given them all a good go, the first two just require checking, but the rest I'm rather stuck on. They're the last questions in about 20 other ones, and my head now hurts. :(

Any hints are very much appreciated!

## Homework Statement

17. Metal X has a work function of 5.0 eV and is used in a demonstration of the photoelectric effect.
a) What is the min. frequency needed to remove electrons from X?

I firstly got converted the 5eV to joules which gave m 8 x 10-19. I then divided that by the planck's constant to get my final answer of 1.21 x 1015Hz

b) What is the wavelength of these waves?

I got the wavelength of 2.49 x 10-7, by dividing the speed of an EM wave by the answer to A.

c) If metal X was irradiated with EM waves of frequency 2.0 x 1015 Hz, what will be the maximum kinetic energy of the photoelectrons released?

I'm afraid this is where I get stuck. The possible equations that I know are KE = 0.5mv2 and hf = φ + ½ mv2max but here I am unsure of the theory. :(

18. In the following two situations, calculate the de Broglie wavelength and, hence, state whether the particle or the wave model should be used.
a) Neutrons (m=1.8x10-28kg) moving at 107ms-1 passing a gap of 8x10-10m

Pretty sure this is the particle model. Unsure of how to calculate the wavelength though, any ideas?

b) Electrons with a momentum of 4x10-19kgms-1 passing nuclei diameter 10-15m

I'm pretty sure this is the wave model. Same as the previous question.