When a thin transparent plate of thickness t and refractive index $\mu$ is placed in the path of one of the two interfering waves of light, then the extra path difference created between two waves due to the plate is

1.  $\left(\mu + 1\right)t$

2.  $\left(\mu - 1\right)t$

3.  $\left(\frac{\mu +1}{t}\right)$

4.  $\mu$t

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

In Young's double-slit experiment, the slit separation is made 3 fold. The fringe width becomes

1.  $\frac{1}{9}$ times

2.  $\frac{1}{3}$ times

3.  9 times

4.  3 times

Wavefront is:

1.  locus of all adjacent points at which the phase of vibration of a physical quantity associated with the wave in the same

2.  locus of all adjacent points at which the electric field is the same

3.  series of points on the wave with the same amplitude

4.  series of points on the wave with the same frequency

Huygens' wave theory allows us to know the:

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

1.		2.
3.		4.

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

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

In a YDSE, let X and Y be the upper and lower slits. A thin film of thickness t and refractive index $\mu$ is placed in front of X. Let $\beta$ = fringe width. The central maximum will shift 

1.  Downward

2.  Upward

3.  By $\left(\mathrm{\mu }-1\right)\mathrm{t}\frac{\mathrm{\beta }}{\mathrm{\lambda }}$

4.  Both (2) & (3)

Given below are two statements: