Question

How many photons of 1.6eV energy would it take to emit an electron from a sheet of metal with ionization energy of 4.0eV?

Answer 1

Answer:

Given : e=1.6×10  

−19

C, c=3×10  

8

m/s

            ϕ=4.2eV, h=6.63×10  

−34

J.s, V  

S

​

=3V

            ϕ=4.2×1.6×10  

−19

J

                =6.72×10  

−19

J

(a) Threshold wavelength =λ  

0

​

=  

ϕ

hc

​

 

                                         =  

6.72×10  

−19

 

6.63×10  

−34

×3×10  

8

 

​

 

                                         =2.960×10  

−7

m

                                         =2960  

A

˚

 

(b) Maximum kinetic energy,

    KE  

max

​

=eV  

S

​

=1.6×10  

−19

×3

              =4.8×10  

−19

J

Explanation: