Quantum mechanics.

  • Thread starter pyxolo
  • Start date
  • #1
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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.

[tex]\[E = \phi + Ec\][/tex]

Regarding to Einstein's equation of photoelectric effect:

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

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

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

Is everything alright?
 
Last edited:

Answers and Replies

  • #2
phyzguy
Science Advisor
4,716
1,635
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.
 
  • #3
2
0
lol, I didn't notice, [tex]\[
1eV = 1.602\cdot10^{ - 19} J
\]
[/tex]
 

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