In fig., light of wavelength `lambda = 5000 Å` is incident on the slits (in a horizontally fixed place).
Here, `d = 1 mm` and `D = 1 m`
Take origin at O and XY plane as shown in the figure. The screen is released from rest from the initial position as shown

The velocity of central maxima at `t = 5 `s is

Options

A. `50 m s^(-1)` along Y-axis
B. `50 m s^(-1)` along negative Y-axis
C. `25 m s^(-1)` along Y-axis
D. `3 xx 10^(8) m s^(-1)` along Y-axis

Answer

a

Explanation

At any time t, the situation ia as shown in the figure below.
Central maxima is always lying on y-axis at `P_(0)`. Its velocity at any time t is given by v p gt along positive Y-axis. So, required velocity is `50 m s^(-1)`