If the sodium light in Young’s double slit experiment is replaced by red light, the fringe width will

(1) Decrease

(2) Increase

(3) Remain unaffected

(4) First increase, then decrease

In Young’s double-slit experiment the wavelength of light was changed from 7000 Å to 3500 Å. While doubling the separation between the slits which of the following is not true for this experiment:

(1) The width of the fringes changes

(2) The colour of bright fringes changes

(3) The separation between successive bright fringes changes

(4) The separation between successive dark fringes remains unchanged

In Young’s double-slit experiment, an interference pattern is obtained on a screen by a light of wavelength 6000 Å, coming from the coherent sources S₁ and S₂. At certain point P on the screen third dark fringe is formed. Then the path difference S₁P – S₂P in microns is 

(1) 0.75

(2) 1.5

(3) 3.0

(4) 4.5

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. 0.32°

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 star emitting light of wavelength 5896 Å is moving away from the earth with a speed of 3600 km/sec. The wavelength of light observed on earth will 

(1) Decrease by 5825.25 Å

(2) Increase by 5966.75 Å

(3) Decrease by 70.75 Å

(4) Increase by 70.75 Å

(c = 3 × 10⁸ m/sec is the speed of light)

A heavenly body is receding away from the earth such that the fractional change in λ is 1, then its velocity is :

(1) C

(2) $\frac{3C}{5}$

(3) $\frac{C}{5}$

(4) $\frac{2C}{5}$

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

The 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. $a\sin \theta =\frac{3\lambda }{2}$