In young's double slit experiment the separation `d` between the slits is `2mm`, the wavelength `lambda` of the light used is `5896 Å` and distance `D` between the screen and slits is `100 cm`. It is found that the angular width of the fringes is `0.20^(@)`. To increases the fringe angular width to `0.21^(@)`(with same `lambda` and `D`) the separtion between the slits needs to be changed to

Options

A. 1.8 mm
B. 1.9 mm
C. 2.1 mm
D. 1.7 mm

Answer

B

Explanation

`theta= (lambda)/(d), (theta_(1))/(theta_(2))= (d_(2))/(d_(1))`
`(0.2)/(0.21)=(d_(2))/(2) implies d_(2)= (0.2)/(0.21) xx 2= 1.9 mm`