What speed should a galaxy move with respect to us so that the sodium line at 589.0 nm is observed at 589.6 nm?

1. 164 km/s

2. 332 km/s

3. 102 km/s

4. 306 km/s

Which one of the following is incorrect?

Two slits are made one millimetre apart and the screen is placed one meter away. What is the fringe separation when blue-green light of wavelength \(500\) nm is used? 
1. \(0.5\) mm
2. \(0.3\) mm
3. \(0.05\) mm
4. \(0.03\) mm

The expression for intensity (as shown in the figure) of transmitted light when a polaroid sheet is rotated between two crossed polaroids is:
[Given: \(I_0\) is the intensity of transmitted light from polariser \(\mathrm{A}\)]

Unpolarised light is incident on a plane glass surface. What should be the angle of incidence so that the reflected and refracted rays are perpendicular to each other?

$1. {45}^0$
$2. {67}^0$
$3. {57}^0$
$4. {37}^0$

Consider the following statements and then mark the incorrect statement/s.

1. Only b and c
2. Only a
3. Only a, b and c
4. All of the above

Two slits are made one millimetre apart and the screen is placed one metre away. What should the width of each slit be to obtain \(10\) maxima of the double-slit pattern within the central maximum of the single-slit pattern?
1. \(2~\text{mm}\)
2. \(0.2~\text{mm}\)
3. \(0.02~\text{mm}\)
4. \(20~\text{mm}\)