39Threshold frequency = c/w = c/(600 x 10-9)
= 0.5 x 1015 = 5 x 1014 Hz
Frequency of incident radiation = c/W = c/(400 x 10-9)
= 0.75 x 1017 Hz = 75 x 1015 Hz
E = hc/W - hc/w = 1/2(mv2)
So (D)?
A metallic surface has a threshold wavelength of 600 nm. It is irradiated by a monochromatic light of wavelength 400 nm. Then,
(A)no photoelectrons are emitted
(B)photoelectrons with speed varying from 0 to V max are emitted
(C)photoelectrons with speed varying from zero to certain fixed value are emitted
(D)photoelectrons, all with speed ,
are emitted
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4 Answers
39
1not all photoelectrons r emitted with max .speed..
only those on the surface of the metal are emitted with max speed, those electrons which is inside the metal surface need some extra energy to come up to d surface, so the value of speed varies frm 0 to a fixd internal, 'c' is right,
but wat is Vmax in B?
B also looks right
29@Rahul
Ya B also looks ryt but it isnt ryt...coz there is some mistake in the statement..
read the options B and C carefully .. u will get it...i thot it's just an easy question but it turned out to be a conceptual one...
if no one comes up with a suitable reason...then i will post my answer.. let's wait till evening..