Question

(a) Write three characteristic features to distinguish between the interference fringes in Young's double slit experiment and the diffraction Pattern obtained due to a narrow single slit. 

(b) A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1 m away. It is observed that the first minimum is at distance of 2.5 mm away from the centre. Find the width of the slit.

Answer 1

(a)

S.No.	Interference	Diffraction
(i)	The width of central maxima is same as that of the other fringes.	The width of central maxima is more than of the other fringes.
(ii)	All bright fringes are of equal intensity.	The intensity of secondary maxima keeps on decreasing.
(iii)	Large number of fringes.	Only a small number of fringes.

(b)