Question

A light source emits light in its rest system of 4000 Angstroms wavelength at the

violet end of the visible spectrum. If in a second system, the light goes perpendicular

to the relative velocity and has a wavelength of 7000 Angstroms at the red end of the

visible spectrum, what is the relative velocity?​

Answer 1

Answer:

We know that,

Maximum energy of emitted photon electron

K.E energy of the incident radiation –work function

Energy of the incident radiation =

λ

hc

Now,

=

λ

hc

=

4000×10

−10

×1.6×10

−19

6.6×10

−34

×3×10

8

=12.37eV

Now, the kinetic energy is

K.E=12.37−2

K.E=10.37eV

Hence, the kinetic energy is 10.37 eV