Question

If intensity of both slits is equal, then ratio of intensity at the centre of a bright fringe to intensity at a point on quarter of the distance between two fringes from the centre is –

• A. 2
• B. 1/2
• C. 4
• D. 16

Answer 1

Answer: (A)

2

Answer 2

Phase difference between two successive fringes is 2p, the phase difference between two points separated by distance equal to one quarter of the distance between two successive fringes is equal to

f = 2p $\left( \frac{1}{4} \right) = \frac{\pi}{2}$

\ I = I_max cos² $\frac{\pi/2}{2}$

\ $\frac{I}{I_{\max}}$ = 2.