In Young’s double-slit experiment the fringe width is β. If entire arrangement is placed in a liquid of refractive index n, the fringe width becomes 

(1) $\frac{\beta }{n+1}$

(2) nβ

(3) $\frac{\beta }{n}$

(4) $\frac{\beta }{n-1}$

In Young’s double slit experiment, distance between two sources is 0.1 mm. The distance of screen from the sources is 20 cm. Wavelength of light used is 5460 Å. Then angular position of the first dark fringe is 

(1) 0.08°

(2) 0.16°

(3) 0.20°

(4) 0.313°

In a Young’s double slit experiment, the slit separation is 0.2 cm, the distance between the screen and slit is 1m. Wavelength of the light used is 5000 Å. The distance between two consecutive dark fringes (in mm) is 

(1) 0.25

(2) 0.26

(3) 0.27

(4) 0.28

A slit of width a is illuminated by white light. For red light (λ = 6500 Å), the first minima is obtained at θ = 30°. Then the value of a will be 

(1) 3250 Å

(2) 6.5 × 10^–4 mm

(3) 1.24 microns

(4) 2.6 × 10^–4 cm

What will be the angular width of central maxima in Fraunhoffer diffraction when light of wavelength $6000\AA$ is used and slit width is 12×10^–5 cm 

(1) 2 rad

(2) 3 rad

(3) 1 rad

(4) 8 rad

A beam of light of wavelength 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of the central bright fringe is 

(1) 1.2 mm

(2) 1.2 cm

(3) 2.4 cm

(4) 2.4 mm

Direction of the first secondary maximum in the Fraunhofer diffraction pattern at a single slit is given by (a is the width of the slit) 

(1) $a\sin \theta =\frac{\lambda }{2}$

(2) $a\cos \theta =\frac{3\lambda }{2}$

(3) $a\sin \theta =\lambda$

(4) $a\sin \theta =\frac{3\lambda }{2}$

A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the first minimum of the diffraction pattern, the phase difference between the rays coming from the edges of the slit is

(1) $0$

(2) $\frac{\pi }{2}$

(3) $\pi$

(4) 2$\pi$

A parallel beam of monochromatic light of wavelength 5000 Å is incident normally on a single narrow slit of width 0.001 mm. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to 

(1) 0^o

(2) 15^o

(3) 30^o

(4) 60^o

In the far field diffraction pattern of a single slit under polychromatic illumination, the first minimum with the wavelength ${\lambda }_1$ is found to be coincident with the third maximum at ${\lambda }_2$. So

(1) $3{\lambda }_1=0.3{\lambda }_2$

(2) $3{\lambda }_1={\lambda }_2$

(3) ${\lambda }_1=3.5{\lambda }_2$

(4) $0.3{\lambda }_1=3{\lambda }_2$