Question

The threshold wavelength for photoelectric emission from a material is
4800 A photelectrons will be emitted
from the material when it is illu-
minated with light from a
a) 40 W blue lamp
b) 40W green lamp
c)100W red lamp
d)100W yellow lamp
e)1000W green lamp​

Answer 1

refer to the above picture

may be it helps you.....

all the best for your future friend..

Answer 2

Answer:

a) 40 W blue lamp.

Explanation:

We know, no photoelectric emission occurs if

wavelength of incident light> threshold wavelength

So, wavelength should be less than 4800 A in this question.

In VIBGYOR, as we go from violet to red wavelength increases.

So, blue lamp having minimum wavelength will emit photoelectrons.