Q. No.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?
| 1. | When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency as the incident frequency. |
| 2. | When light travels from a rarer to a denser medium, the speed decreases. The reduction in speed implies a reduction in the energy carried by the light wave. |
| 3. | In the wave picture of light, the intensity of light is determined by the square of the amplitude of the wave. |
| 4. | For a given frequency, the intensity of light in the photon picture is determined by the number of photons crossing a unit area per unit time. |
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
Assume that light of wavelength 6000Å is coming from a star. What is the limit of resolution of a telescope whose objective has a diameter of 100 inches?
For what distance is ray optics a good approximation when the aperture is \(3\) mm wide and the wavelength is \(500\) nm?
1. \(32\) m
2. \(42\) m
3. \(18\) m
4. \(20\) m
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 \(\mathrm{A}\)]
| 1. | \(I = \dfrac{I_{0}}{2} \sin^{2} 2 \theta\) | 2. | \(I = \dfrac{I_{0}}{4} \sin^{2} 2 \theta\) |
| 3. | \(I = \dfrac{I_{0}}{2} \cos^{2} 2 \theta\) | 4. | \(I = \dfrac{I_{0}}{4} \cos^{2} 2 \theta\) |
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?
Consider the following statements and then mark the incorrect statement/s.
| a. | The angular separation of the fringes increases if the screen is moved towards the plane of the slits. |
| b. | The angular separation of the fringes increases if the (monochromatic) source is replaced by another (monochromatic) source of a shorter wavelength. |
| c. | The angular separation of the fringes increases if the separation between the two slits is increased. |
| d. | The sharpness of the fringes increases when the source slit is moved closer to the double-slit plane. |
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. \(20~\text{mm}\)
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. | \(\dfrac{3\pi}{2}\) | 4. | \(\dfrac{\pi}{2}\) |
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