When the light diverges from a point source, the shape of the wavefront is:

1. Parabolic.

2. Plane.

3. Spherical.

4. Elliptical.

Which of the following is not true?

The resolving power of a compound microscope will be maximum when:

If the light is polarised by reflection, then the angle between reflected and refracted light is:

1. $\pi$

2. $\pi$/2

3. 2$\pi$

4. $\pi$/4

Two sources with intensity I_o and 4I_o respectively interfere at a point in a medium. The maximum and the minimum possible intensity respectively would be:
1. 2I_o, I_o
2. 9I_o, 2I_o
3. 4I_o, I_o
4. 9I_o, I_o

The relation between the fringe width for the red light and yellow light is: (all other things being the same.)

$1. {\beta }_{red}<{\beta }_{yellow}$
$2. {\beta }_{red}>{\beta }_{yellow}$
$3. {\beta }_{red}={\beta }_{yellow}$
$4. {\beta }_{red}=2{\beta }_{yellow}$

Fringe width in a particular YDSE is measured to be $\beta$. What will be the fringe width if the wavelength of the light is doubled, the separation between the slits is halved and the separation between the screen and slits is tripled?

1. 10 times

2. 11 times

3. Same

4. 12 times

In YDSF the slits are separated by 0.28 mm and the screen is placed 1.4 m away. The distance between the first dark fringe and the fourth bright fringe is obtained to be 0.6 cm. The wavelength of the light used in the experiment is:

$1.$ $3.4\times {10}^{-7}$ $m$
$2.$ $4.1\times {10}^{-7}$ $m$
$3.$ $3.4\times {10}^{-9}$ $m$
$4.$ $4.1\times {10}^{-9}$ $m$

Light of wavelength 6328 $\stackrel{\circ }{A}$ is incident normally on a slit having a width of 0.2 mm. The width of the central maximum measured from minimum to minimum of diffraction pattern on a screen 9 m away will be nearly:

1. 0.36^o

2. 0.18^o

3. 0.72^o

4. 0.09^o

The first diffraction minima due to a single slit diffraction is at $\mathrm{\theta } = 30°$for a light of wavelength  \(5000~\mathring A.\)  The width of the slit is:

1. 5 x 10^-5 cm

2. 10 x 10^-5 cm

3. 2.5 x 10^-5 cm

4. 1.25 x 10^-5 cm