Question

Sun light is diffracted through a circular aperture of diameter 0.1μm. If diameter is slightly increased then

(1) Size of circular fringe will increase, intensity decrease.

(2) Size of circular fringe will decrease, intensity increase.

(3) Size of circular fringe will increase, intensity increase.

(4) Size of circular fringe will decrease, intensity decrease.

Comments

Wave optics, Diffraction due to a circular aperture

Answer 1

Ans. (2) Size of circular fringe will decrease, intensity increase.

Sol. $\sin\theta ={1.22\lambda\over D}$

$\implies$ If D is increased $\implies\sin\theta$ decreased

$\therefore$ size of circular fringe will decrease

Intensity will increase.