Question

In Young's double-slit experiment, if the two slits are illuminated with separate sources, no interference pattern is observed why?

Answer 1

Step 1: Young's double hole experiment

1. Light waves from a monochromatic light source are irradiated via two slits separated by a distance d in Young's double-slit experiment.
2. At a distance D, a screen is erected parallel to the two slits, such that the consequent wave of new strength is created when the two waves interfere at a place on the screen.
3. The light's intensity is determined by the path difference between the two waves. As a result, the screen displays a pattern of bright and dark fringes in succession.
4. Bright fringe denotes the point with the most intensity, while dark fringe denotes the point with the lowest intensity.

Step 2: Analysing

1. In young's double-slit experiment, the light is coherent.
2. Two waves are coherent when they have a constant relative phase or when they have zero or constant phase difference and the same frequency.
3. If there is no interference pattern that means the phase difference would have not been constant.
4. For only 10-9 seconds, light from two slits will have a fixed phase connection. As a result, every interference pattern generated on the screen would only last 10-9 seconds before changing.
5. We won't be able to discern any interference pattern since the human eye can only detect intensity fluctuations that last at least a tenth of a second.
6. Instead, we will only see a uniform intensity across the screen due to quick changes in the pattern.

Hence, In Young's double-slit experiment, if the two slits are illuminated with separate sources, no interference pattern is observed because there will be no constant phase difference between the two waves.