Q. No.Two beams, \(A\) and \(B\), of plane-polarized light with mutually perpendicular planes of polarization are seen through a Polaroid. From the position when beam \(A\) and has maximum intensity (and beam \(B\) has zero intensity), a rotation of polaroid through \(30^\circ\) makes the two beams appear equally bright. If the initial intensities of the two beams are \(I_A\) and \(I_B\) respectively, then \(\frac{I_A}{I_B}\) equals:
1. \(\frac{3}{2}\)
2. \(1\)
3. \(\frac{1}{3}\)
4. \(3\)
On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens' principle leads us to conclude that as it travels, the light beam:
| 1. | becomes narrower |
| 2. | goes horizontally without any deflection |
| 3. | bends downwards |
| 4. | bends upwards |
1. \(|{p}_{y}|{d > h}\)
2. \(|{p}_{y}|{d \gg h}\)
3. \(|{p}_{y}|{d < h}\)
4. \(|{p}_{y}|{d \simeq h}\)
1. \(\beta\over 6\)
2. \(\beta\over 3\)
3. \(\beta\over 4\)
4. \(\beta\over 2\)
| 1. | the reflected light is completely polarized with an intensity of less than \({I_0\over 2}\) |
| 2. | transmitted light is completely polarized with an intensity of less than \({I_0\over 2}\) |
| 3. | transmitted light is partially polarized with intensity \({I_0\over 2}\) |
| 4. | the reflected light is partially polarized with intensity \({I_0\over 2}\) |
In a Young’s double slit experiment, slits are separated by \(0.5~\text{mm}\), and the screen is placed \(150~\text{cm}\) away. A beam of light consisting of two wavelengths, \(650~\text{nm}\) and \(520~\text{nm}\), is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is:
1. \(1.56~\text{mm}\)
2. \(7.8~\text{mm}\)
3. \(9.75~\text{mm}\)
4. \(15.6~\text{mm}\)
(i.e. distance between the first minimum on either side of the central maximum)
1. \(4.5~\text{cm}\)
2. \(6.0~\text{cm}\)
3. \(3.0~\text{cm}\)
4. \(1.5~\text{cm}\)
1. \(3~\text{mm}\)
2. \(1.5~\text{mm}\)
3. \(9~\text{mm}\)
4. \(4.5~\text{mm}\)
Unpolarized light of intensity \(I\) passes through an ideal polarizer \(A\). Another identical polarizer \(B\) is placed behind \(A\). The intensity of light beyond \(B\) is found to be \(\frac{I}{2}\). Now another identical polarizer \(C\) is placed between \(A\) and \(B\). The intensity beyond \(B\) is now found to be \(\frac{I}{8}\). The angle between the polarizer \(A\) and \(C\) is:
1. \(0^\circ\)
2. \(30^\circ\)
3. \(45^\circ\)
4. \(60^\circ\)
The angular width of the central maximum in a single slit diffraction pattern is \(60^\circ\). The width of the slit is \(1~\mu\text{m}\). The slit is illuminated by monochromatic plane waves. If another slit of same width is made near it, Young's fringes can be observed on a screen placed at a distance \(50~\text{cm}\) from the slits. If the observed fringe width is \(1~\text{cm}\), what is the slit separation distance? (i.e. distance between the centers of each slit.)
1. \(25~\mu\text{m}\)
2. \(50~\mu\text{m}\)
3. \(75~\mu\text{m}\)
4. \(100~\mu\text{m}\)
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