Two coherent sources of light interfere and produce fringe patterns on a screen. For the central maximum, the phase difference between the two waves will be: 
1. zero 
2. \(\pi\)
3. \(\frac{3\pi}{2}\)
4. \(\frac{\pi}{2}\)$$

For a crystal with λ = 1 Å and Bragg's angle θ = 60°, the second-order diffraction, 'd' (distance between two consecutive atomic layers) will be:
1.  1.15 Å
2.  0.75 Å
3.  0.55 Å
4.  2.1 Å

The interplanar distance in a crystal is \(2.8 \times 10^{-8} \) m. The value of the maximum wavelength which can be diffracted:

1. \(2.8 \times 10^{-8} \)$m$

2. \(5.6 \times 10^{-8} \)$m$

3. \(1.4 \times 10^{-8} \)$m$

4. \(7.6 \times 10^{-8} \)$m$

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, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes:

A linearly polarized monochromatic light of intensity \(10\) lumen is incident on a polarizer. The angle between the direction of polarization of the light and that of the polarizer such that the intensity of output light is \(2.5\) lumen is:

A monochromatic light of frequency \(500\) THz is incident on the slits of a Young's double slit experiment. If the distance between the slits is \(0.2\) mm and the screen is placed at a distance \(1\) m from the slits, the width of \(10\) fringes will be:
1. \(1.5\) mm
2. \(15\) mm
3. \(30\) mm
4. \(3\) mm