Question

Consider the following statements in case of Young's double slit experiment.
1. A slit S is necessary if we use an ordinary extended source of light.
2. A slit is S not needed if we use an ordinary but well collimated beam of light.
3. A slit S is not needed if we use a spatially coherent source of light.
Which of the above statements are correct ?

• A. (1), (2) and (3)
• B. (1), and (2) only
• C. (2) and (3) only
• D. (1) and (3) only

Answer 1

Answer: (A)

(1), (2) and (3)

In order to obtain the interference pattern, the light source should be coherent. The coherent source can be produced in all three manners.

An extended source of light placed behind the slit will produce light of different wavelengths. The slit will convert it to coherent light.

A well-collimated beam of light has a constant frequency and wavelength and therefore, it is used as a coherent source.

If the source is itself coherent, then no slit is required for the interference of light.

So, option $\left(1\right),\left(2\right)and\left(3\right)$ are correct.