Question

Why won’t two small sodium lamps, held close together, produce an interference pattern on a distant screen? What if the sodium lamps were replaced by two laser pointers held close together?

a. Sodium lamps produce incoherent light; laser pointers produce coherent light.
b. Both sodium lamps and laser pointers produce incoherent light.
c. Interference depends on the separation, not the light source.
d. Sodium lamps and laser pointers produce identical interference patterns.

Answer 1

Sodium lamps produce incoherent light, while laser pointers produce coherent light, which can result in an interference pattern. Hence, option (a) is correct.

Step-by-step explanation:

The reason why two small sodium lamps, held close together, won't produce an interference pattern on a distant screen is because sodium lamps produce incoherent light, which means the waves emitted by each lamp do not have a definite phase relationship. Interference patterns can only be formed when coherent light sources are used.

If the sodium lamps were replaced by two laser pointers held close together, an interference pattern would be observed. Laser pointers produce coherent light where the waves emitted by each laser have a definite phase relationship.

On the other hand, laser light is highly coherent. Laser light waves have a well-defined and constant phase relationship, making them suitable for producing interference patterns.