Huygen's principle for secondary wavelets may be used to:

1.	explain Snell's law.
2.	find the velocity of light in vacuum.
3.	find a new position of a wavefront.
4.	both (1) & (3) are correct.

A beam of unpolarized light of intensity $I_0$ is passed first through a tourmaline crystal A and then through another tourmaline crystal B oriented so that its principal plane is parallel to that of A. The intensity of the final emergent light is I. The value of I is:

1.  $I_0$

2.  $\frac{I_0}{2}$

3.  $\frac{I_0}{4}$

4.  $\frac{I_0}{8}$

In YDSE, an electron beam is used to obtain an interference pattern. If the speed of electrons is increased:

The graph between resolving power and accelerating potential V for an electron microscope is (P is resolving power):

1.		2.
3.		4.

Huygens' wave theory allows us to know the:

Two coherent sources are 0.3 mm apart. They are 1 m away from the screen. The second dark fringe is at a distance of 0.3 cm from the center. The distance of the fourth bright fringe from the centre is:

1.  0.6 cm

2.  0.8 cm

3.  1.2 cm

4.  0.12 cm

If the ratio of amplitudes of two coherent sources producing an interference pattern is 3 : 4, the ratio of intensities at maxima and minima is:

1.  3 : 4

2.  9 : 16

3.  49 : 1

4.  25 : 7

Young's double-slit experiment is performed in a liquid. The 10^th bright fringe in the liquid lies where the 8th dark fringe lies in a vacuum. Refractive index of the liquid is approximately:

1.  1.81

2.  1.67

3.  1.54

4.  1.33

The resolving power of a microscope can be increased by using:

1.  red light.
2.  blue light.
3.  oil between objective lens and object.
4.  both (2) and (3).

If the 5th order maxima of wavelength 4000 $\stackrel{\mathrm{o}}{\mathrm{A}}$ in Young's double-slit experiment coincides with the nth order maxima of wavelength 5000 $\stackrel{\mathrm{o}}{\mathrm{A}}$, then n is equal to:

1.  5

2.  8

3.  4

4.  10