Question

The slits in a Young's double slit experiment are illuminated by two different wavelengths ${\lambda }_1$ and ${\lambda }_2$. A thin film is placed in front of the slit $S_1$, which blocks ${\lambda }_1$ and allows ${\lambda }_2$ to pass. Another thin film is placed in front of $S_2$ such that it blocks ${\lambda }_2$ and allows ${\lambda }_1$ to pass. Then, on the screen, we will observe

• A. an interference pattern due to both ${\lambda }_1$ and ${\lambda }_2$
• B. an interference pattern due to ${\lambda }_1$ only, which is shifted along $S_1$
• C. an interference pattern due to ${\lambda }_2$ only, which is shifted along $S_2$
• D. no interference pattern

Answer 1

The correct option is D no interference pattern

As a result of both the films, the two slits are sources of two different wavelengths, ${\lambda }_1$ and ${\lambda }_2$. This means that $S_1$ and $S_2$ are now non-monochromatic sources. So, no interference pattern will be obtained.

Hence, $\left(D\right)$ is the correct answer.