On superposition of two waves \(y_{1}=3sin\left ( \omega t-kx \right )\) and \(y_{2}=4sin\left ( \omega t-kx+\frac{\pi }{2} \right )\) at a point, the amplitude of the resulting wave will be:

1.  7

2.  5

3.  $\sqrt{7}$

4.  6.5

In Young's double-slit experiment using the light of wavelength '$\lambda$', 60 fringes are seen on a screen. If the wavelength of light is decreased by 50%, then the number of fringes on the same screen will be:

1.  30

2.  60

3.  120

4.  90

If the polarising angle for a material is $60°$, then the refractive index of the material will be:

1.  $\frac{1}{\sqrt{3}}$

2.  $\frac{3}{2}$

3.  $\sqrt{3}$

4.  $\frac{\sqrt{3}}{2}$

Five identical polaroids are placed coaxially with \(45^{\circ}\) angular separation between pass axes of adjacent polaroids as shown in the figure. (I₀: Intensity of unpolarized light)
          
The intensity of light, I, emerging out of the 5^th polaroid is:

1.  $\frac{{\mathrm{I}}_0}{4}$

2.  $\frac{{\mathrm{I}}_0}{8}$

3.  $\frac{{\mathrm{I}}_0}{16}$

4.  $\frac{{\mathrm{I}}_0}{32}$

In Y.D.S.E., the ratio of maximum intensity at a point to the intensity at the same point when one slit is closed, is:

1. 2

2. 3

3. 4

4. 1

Two light sources are said to be coherent when their:

Which statement is true for interference?

Light waves of intensities \(I\) and \(9I\) interfere to produce a fringe pattern on a screen. The phase difference between the waves at point P is $\frac{3\mathrm{\pi }}{2}$ and 2$\mathrm{\pi }$ at other point Q. The ratio of intensities at P and Q is:

1.  8: 5

2.  5: 8

3.  1: 4

4.  9: 1

In Young's double-slit experiment sources of equal intensities are used. The distance between the slits is d and the wavelength of light used is $\lambda$($\lambda$<<d). The angular separation of nearest points on either side of central maximum where intensities become half of the maximum value is:

1.  $\frac{\lambda }{d}$

2.  $\frac{\lambda }{2d}$

3.  $\frac{\lambda }{4d}$

4.  $\frac{\lambda }{6d}$

Four coherent sources of intensity \(I\) are superimposed constructively at a point. The intensity at that point is:

1. \(4I\)
2. \(8I\)
3. \(16I\)
4. \(24I\)