In young's experiment, the wavelength of red light is $7.8\times {10}^{-5}$ cm and that of blue light $5.2\times {10}^{-5}$ cm. The value of n for which (n+1)th blue bright band coincides with the nth red band is:

1. 4

2. 3

3. 2

4. 1

The Brewster's angle for an interface should be:
1. \(30^{\circ}<i_b<45^{\circ}\)
2. \(45^{\circ}<i_b<90^{\circ}\)
3. \(i_b=90^{\circ}\)
4. \(0^{\circ}<i_b<30^{\circ}\)

In Young’s double-slit experiment, the slits are separated by \(0.28~\text{mm}\) and the screen is placed \(1.4 ~\text m\) away. The distance between the central bright fringe and the fourth bright fringe is measured to be \(1.2~\text{cm}.\) The wavelength of light used in the experiment is:
1. \(600~\text{nm}\)
2. \(500~\text{nm}\)
3. \(400~\text{nm}\)
4. \(200~\text{nm}\)

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 \(1 ~\text{m}\) away. The wavelength of light used is \(600 ~\text{nm}.\) 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

The resolving power of an electron microscope is \(R,\) when the accelerating potential is \(V.\) If the accelerating potential is increased by \(3V,\) then it's new resolving power is:
1. \(3R\)
2. \(2R\)
3. \(4R\)
4. \(R\)

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