Question

A concave mirror of radius of curvature 10 cm is cut into two equal parts, slightly separated and placed in front of a monochromatic line source S of wavelength 2000 $\hat{A}$ as shown in figure. Consider only interference in reflected light after first reflection from mirrors. Assume direct light from S is blocked from reaching the screen

If half of reflecting surface of upper part of mirror is painted black then choose correct option

• A. Intensity of maxima and minima will both decrease
• B. Intensity at minima will increase and at maxima intensity will decrease.
• C. Position of first order minima will move closer to the center of screen
• D. Position of first order minima will change.

Answer 1

The correct option is B

Intensity at minima will increase and at maxima intensity will decrease.

As half reflecting surface of one part is painted black then intensity of one surface will decrease so intensity at maxima will decrease and at minima it will increase(when intensity of both sources is same then there is zero intensity at minima).