Question

In a Young's double slit experiment, the separation between the two slits is $d$ and the wavelength of the light is $\lambda$. The intensity of light falling on slit 1 is four times the intensity of light falling on slit 2. Choose the correct choice(s).

• A. If $d=\lambda$, the screen will contain only one maximum
• B. If $\lambda <d<2\lambda$, at least one more maximum (besides the central maximum) will be observed on the screen
• C. If the intensity of light falling on slit 1 is reduced so that it becomes equal to that of slit 2, the intensities of the observed dark and bright fringes will increase
• D. If the intensity of light falling on slit 2 is increased so that it becomes equal to that of slit 1, the intensities of the observed dark and bright fringes will increase

Answer 1

Answer: (A), (B)

The correct options are
A If $d=\lambda$, the screen will contain only one maximum
B If $\lambda <d<2\lambda$, at least one more maximum (besides the central maximum) will be observed on the screen

For at least one maxima, $\sin \theta =\lambda /d$
If $\lambda =d,\sin \theta =1$ and $y\to \infty$
If $\lambda <d<2d,\sin \theta$ exists and $y$ is finite