In Young’s double-slit experiment, the slits are separated by \(0.28\) mm and the screen is placed \(1.4 \) m away. The distance between the central bright fringe and the fourth bright fringe is measured to be \(1.2\) cm. Determine the wavelength of light used in the experiment.

In Young’s double-slit experiment using monochromatic light of wavelength \(\lambda,\) the intensity of light at a point on the screen where path difference \(\lambda\) is \(K\) units. What is the intensity of the light at a point where path difference is \(\lambda/3\)?
1. \(\dfrac K3\)
2. \(\dfrac K4\)
3. \(\dfrac K2\)
4. \(K\)

In a double-slit experiment the angular width of a fringe is found to be \(0.2^\circ\) on a screen placed \(1\) m away. The wavelength of light used is \(600\) nm. What will be the angular width of the fringe if the entire experimental apparatus is immersed in water?
(Take the refractive index of water to be \(4/3\)).
1. \(0.33^\circ\)
2. \(0.20^\circ\)
3. \(0.15^\circ\)
4. \(0.10^\circ\)

What is the Brewster angle for air to glass transition? (Refractive index of glass = 1.5.)

1. $49.{29}^0$
2. $43.{21}^0$
3. $50.{30}^0$
4. $56.{31}^0$

What is the distance for which ray optics is a good approximation for an aperture of 4 mm and wavelength 400 nm?

1. 40 m
2. 30 m
3. 20 m
4. 50 m

When the light diverges from a point source, the shape of the wavefront is:
1. Parabolic.
2. Plane.
3. Spherical.
4. Elliptical.

When the light is coming from a distant star that is intercepted by the earth, the shape of the wavefront is:

The refractive index of glass is \(1.5\). What is the speed of light in glass? 
1. \(2 \times 10^{8}~\text{m/s}\)
2. \(3 \times 10^{8} ~\text{m/s}\)
3. \(1.5 \times 10^{8} ~\text{m/s}\)
4. \(2.2 \times 10^{8}~\text{m/s}\)

Which of the following is not true?

A beam of light consisting of two wavelengths, \(650\) nm, and \(520\) nm, is used to obtain interference fringes in Young’s double-slit experiment. What is the distance of the third bright fringe on the screen from the central maximum for wavelength \(650\) nm?