Question

In List 1, the nature of light is given and in List 2 the information about the photons are mentioned. Match the entries of List 1 with correct entries in List 2.

$\begin{array}{cccc}& \text{List-1}& & \text{List-2}\\ \text{I}& \text{A bichromatic light source}& \text{P}& \text{Some photons have same energy and momenta}\\ \text{II}& \text{A point source of white light emitting light uniformly in all directions}& \text{Q}& \text{Some photons have different energy and different momenta}\\ \text{III}& \text{A point source of monochromatic light emitting light uniformly in all directions}& \text{R}& \text{Some photons have same energy and different momenta}\\ \text{IV}& \text{Laser light source}& \text{S}& \text{Some photons have different energy and same momenta}\end{array}$

• A. I $\to$ P,Q,R; II $\to$ P,Q,R,S; III $\to$ P,R; IV $\to$ P
• B. I $\to$ P,Q,R,S; II $\to$ Q,R,S; III $\to$ P,R; IV $\to$ P,Q
• C. I $\to$ P,Q,R; II $\to$ Q,R,S; III $\to$ P,R; IV $\to$ P
• D. I $\to$ P,Q,R,S; II $\to$ P,Q,R,S; III $\to$ P,R; IV $\to$ P

Answer 1

The correct option is D I $\to$ P,Q,R,S; II $\to$ P,Q,R,S; III $\to$ P,R; IV $\to$ P

(i) Bichromatic light source is having two wavelengths and hence from energy point of view, two types of photons are possible. As light propagates in different directions, the photon can have different or same momenta depending upon the magnitude and direction of photon motion.
(ii) Same reasoning as for (i)
(iii) For a monochromatic light source, all photons have same energy but momenta can be different due to different directions.
(iv) Laser is a very narrow beam of monochromatic light, so all photons have nearly same energy and momenta.