Question

The energy required to dislodge electrons from sodium metal via the photoelectric effect is 275 kJ/mol What wavelength in m of light has sufficient energy to dislodge an electron from the surface of sodium?

Answer 1

I got `430nm`

Explanation:

You need `275kJ` to dislodge one mol of electrons so we need:

`(275xx10^3)/(6xx10^23)=4.6xx10^-19J` for one electron only.

We can use Einstein`s relationship between energy `E` and frequency `f` and between frequency and wavelength `lambda`:

`E=hf=hc/lambda`

to find the wavelength (`h` is Plank`s Constant and `c` the speed of light).
We get:
`lambda=hc/E=(6.6xx10^-34)*(3xx10^8)/(4.6xx10^-19)=4.3xx10^-7m=430nm`