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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 10

^{15}Hz

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 = 0.5mv

^{2}and hf = φ + ½ mv

^{2}

_{max}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^{-28}kg) moving at 107ms^{-1}passing a gap of 8x10^{-10}m

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

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

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

Thanks for reading!