Photoelectric effect threshold

[Nairabhi]

When a cm thick surface is illuminated with light of wavelength lambda,the stopping potential is V. When the same surface is illuminated by light of wavelength 2lambda , the stopping potential is V/3.The threshold wavelength for the surface is ?

Homework Equations

The Attempt at a Solution

 

[Matterwave]

Did you try to do this problem yourself?

 

[Nairabhi]

Did you try to do this problem yourself?

Yes i tried but i am unable to solve it.

 

[NascentOxygen]

Yes i tried but i am unable to solve it.

Hi Nairabhi. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

What equations do you have that you'll use here?

 

[Nairabhi]

Hi Nairabhi. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

What equations do you have that you'll use here?

See according to Einstein equation KE(Max)= Energy of photons - work function of surface, but since work function is not given i have assumed it
to be 0. And energy of photons is equal to hc/lamda and this energy is equal to KE(Max) or the stopping potential so using these equations and i am trying to find a relation between them and find the threshold wavelength .However i don't understand what role does the thickness of surface plays which is 1cm ?

 

[NascentOxygen]

You should assume work function is non-zero, and is fixed at some value.

That material thickness may simply mean "of suitable thickness" for our purposes.

Does the textbook give the correct answer?