The fringe width difference \( \Delta y \) is calculated using the given parameters: \[ \Delta y = \frac{8 \lambda D}{(0.8 - 0.04) \times 10^{-3}} - \frac{8 \lambda D}{(0.8 + 0.04) \times 10^{-3}} \] where:
\[ \Delta y = 601.5 \, \mu \text{m} \]
The fringe width difference due to the variation in slit separation is \( 601.5 \, \mu \text{m} \).
The amplitude of oscillation of the fringe is calculated as: \[ A = \frac{\Delta y}{2} = \frac{601.50 \, \mu \text{m}}{2} \]
The maximum speed of the oscillation is given by: \[ v_{\text{max}} = A \omega \] where \( \omega \) is the angular frequency.
Substitute the values:
\[ v_{\text{max}} = 300.75 \, \mu \text{m} \times 0.08 = 24.06 \, \mu \text{m/s} \]
The maximum speed of the fringe oscillation is \( v_{\text{max}} = 24 \, \mu \text{m/s} \).
If the monochromatic source in Young's double slit experiment is replaced by white light,
1. There will be a central dark fringe surrounded by a few coloured fringes
2. There will be a central bright white fringe surrounded by a few coloured fringes
3. All bright fringes will be of equal width
4. Interference pattern will disappear