Calculate the minimum frequency needed to start the electron

[pyxolo]

Hi there.
I am a student from Spain and I am about to join the University but I have to pass physics at High School.

Here It is:

The work of extracting an Eletron in a metal is 3.8 eV. Calculate the minimum frequency needed to start the electron.

This is what I did.

$$\[E = \phi + Ec\]$$

Regarding to Einstein's equation of photoelectric effect:

$$\[h\nu = h\nu _0 + \frac{1}{2}mv^2 \]$$

When I got to this point, I assumed that the electron's velocity would be zero and then:

$$\[\nu = \frac{{3.8}}{{6.63\cdot10^{ - 34} }} = 5.73\cdot10^{33}$$
Hertzios

Is everything alright?

 

[phyzguy]

No. You have to be more careful with units. You have used the energy in units of eV, and h in units of J-sec. You need to use a consistent set of units - either convert the energy in eV into J, or use h in eV-sec. Try again, and use dimensional analysis to check the units of your answer.

 

[pyxolo]

lol, I didn't notice, $$\[ 1eV = 1.602\cdot10^{ - 19} J \]$$