Work Function, Threshold Frequency.. etc (1 Viewer)

[DementedDonkey]

Anyone know if we need to know this? Our teacher hasn't said anything about this and I'm starting to freak out a bit.

 

[FinalFantasy]

yea, u need to know it... but if ur teacher hasn't taught u it den he\she should take it out of the exam?

 

[DementedDonkey]

what if my teacher just happens to be an idiot? i'm screwed aren't i...

 

[FinalFantasy]

well if ur teacher really just lets the question in... and he hasn't taught it... then ur other class members will also be screwed...
so what's the matter?

and also dat thing isn't that scary anyway....

Consider the case where light is shone onto a metal surface.
The photons in this light carry energy given by Mr Planck's formula E=hf
For this photon to eject electrons out of the metal surface, the energy of that photon must be greater than the "Work Function", which u can just work it out using the same formula E=hf_0
where f_0 is ur "Threshold Frequency"
You can also use the formula C=f*lambda on ur photon to work out it's frequency and compare it to that "Threshold Frequency"
Basically just play around with E=hf, C=f*lambda...

 

[DementedDonkey]

are we going to be given threshold frequency? or do we need to know how to work that out?

 

[FinalFantasy]

as i said... just play around with C=f lambda and E=hf
if ur not given the threshold frequency den u'll probably be given the work function E, in which case u can just do f=E\h and work out that threshold frequency

 

[DementedDonkey]

thanks heaps. have decided to go into school and abuse my teacher. you've calmed me down a bit.

 

[DementedDonkey]

Hmm teacher didnt seem to know anything about it, certainly didnt think it was in the syllabus.. im scared

 

[wanton-wonton]

Hmm teacher didnt seem to know anything about it, certainly didnt think it was in the syllabus.. im scared

The specific term of threshold frequency is not in the syllabus but I guess it's assumed that you know it in order to understand the photoelectric effect which is of course addressed in the syllabus.

 

[wanton-wonton]

Threshold frequency: the minimum frequency of a photon that can eject an electron from a surface

Work function: the minimum energy needed to remove an electron from within a solid to a point outside its surface in a vacuum.

So it can be seen that threshold frequency and work function are a lot alike. In fact, it'd say they're equivalent, just as mass and energy are equivalent.

I might be wrong though.