Question

Two metals A and B have work functions 2eV and 4eV respectively. Which metal has a lower threshold wavelength for photoelectric effect? Explain.

Answer 1

Work function of metal A = 2ev
Work function of metal B= 4ev
Threshold energy is same as work function.
we know that,
hv = W +KE
hv =energy of light incident upon metal
W = work function
By given information it is clear that energy required to remove electron from metal B is more.
Energy of a light is directly proportional to frequency and inversely proportional to its wavelength.
Threshold energy of metal B is more than metal A.

Therefore threshold wavelength of Metal B is less than Metal A.

And frequency of threshold energy of metal B will be more than metal A.

At the same time if same type of light is incident upon both the metals then KE possessed by electrons of Metal B will be less than metal A.