Fringe width due to interference of two coherent sources is $\mathrm{\beta }$. If frequency of sources is tripled, new fringe width will be :-

1. 3$\mathrm{\beta }$

2. $\mathrm{\beta }$ / 3

3. 2$\mathrm{\beta }$

4. $\mathrm{\beta }$ / 2

Two coherent sources of wavelength $\mathrm{\lambda }=6.2\times {10}^{-7} \mathrm{m}$ produce interference. Path difference corresponding to 10^th bright band will be :-

1. 6.2 x 10^-6 m

2. 3.1 x 10^-6 m

3. 1.5 x 10^-6 m

4. 12.4 x 10^-6 m

A window with grills is seen through a telescope at a distance of 200 m. Distance between grill wires is 2 mm. Wavelength of light used is 5000A. Minimun diameter of telescope should be :-

1. 6.1 cm

2. 5.9 cm

3. 2 cm

4. 3.6 cm

Diffraction pattern can be seen :-

1. Only in sound waves

2. Only in light waves

3. Only in ultrasonic waves

4. in sound and light waves

Interference fringes are produced using white light in a double-slit arrangement. When a mica sheet of uniform thickness of the refractive index 1.6 (relative to air) is placed in the path of light from one of the slits, the central fringe moves by a distance.

This distance is equal to the width of 30 interference bands. If the light of wavelength 4800 $\stackrel{\mathrm{o}}{\mathrm{A}}$ is used, the thickness (in $\mu$m) of mica is —

1.  90

2.  12

3.  14

4.  24

In Young's double slit experiment maximum intensity is I than the angular position where the intensity becomes $\frac{1}{4}$ is :

1. ${\sin }^{-1}\left(\frac{\lambda }{d}\right)$

2. ${\sin }^{-1}\left(\frac{\lambda }{3d}\right)$

3. ${\sin }^{-1}\left(\frac{\lambda }{2d}\right)$

4. ${\sin }^{-1}\left(\frac{\lambda }{4d}\right)$

In a mica sheet of thickness t and refractive index $\mathrm{\mu }$ is placed in the path of one of interfering beam in a double slit experiment, then displacement of fringes will be :-

1. $\frac{\mathrm{D}}{\mathrm{d}}\mathrm{\mu t}$

2. $\frac{\mathrm{D}}{\mathrm{d}}(\mathrm{\mu }-1)\mathrm{t}$

3. $\frac{\mathrm{D}}{\mathrm{d}}(\mathrm{\mu }+1)\mathrm{t}$

4. $\frac{\mathrm{D}}{\mathrm{d}}\left({\mathrm{\mu }}^2-1\right)\mathrm{t}$

To demonstrate the phenomenon of interference we require two sources which emit radiations of :

1. nearly the same frequency

2. the same frequency

3. different wavelength

4. the same frequency and having a definite phase relationship

In refraction. light waves are bent on passing from one medium to the second medium, because in the second medium :

1. the frequency is different

2. the coefficient of elasticity is different

3. the speed is different

4. the amplitude is smaller

In a double slit experiment, instead of taking slits of equal widths, one slit is made twice as wide as the other. Then, in the interference pattern :-

1. the intensities of both the maxima and the minima increase

2. the intensity of the maxima increases and the minima has zero intensity

3. the intensity of the maxima decreases and that of the minima increases

4. the intensity of the maxima decreases and the minima has zero intensity