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Q. No.Consider sunlight incident on a slit of width \(10^{4}~\mathring{A}.\) The image seen through the slit shall:
| 1. | be a fine sharp slit white in colour at the centre |
| 2. | a bright slit white at the centre diffusing to zero intensities at the edges |
| 3. | a bright slit white at the centre diffusing to regions of different colours |
| 4. | only be a diffused slit white in colour |
Subtopic: Â Diffraction |
Level 4: Below 35%
Hints
White light is used to illuminate the double slit in Young's double-slit experiment. Which of the following is/are true?
1. I only
2. I, II
3. I, III
4. I, II, III
| I. | The central fringe will be white. |
| II. | Closest bright fringe to the central fringe will be a violet fringe. |
| III. | There will not be any dark fringe. |
2. I, II
3. I, III
4. I, II, III
Subtopic: Â Young's Double Slit Experiment |
Level 3: 35%-60%
Hints
A light beam traveling along the \(x\text-\)axis with a planar wavefront is incident on a medium of thickness \(t\). In the region, where light is falling, the refractive index can be taken to be varying such that \(\dfrac{dn}{dy}>0.\) The light beam on the other side of the medium will emerge:
| 1. | parallel to the \(x\text-\)axis |
| 2. | bending downward |
| 3. | bending upward |
| 4. | split into two or more beams |
Subtopic: Â Huygens' Principle |
Level 3: 35%-60%
Hints
Light of wavelength \(\lambda\) falls perpendicularly onto a single slit of width \(d\). A diffraction maximum is formed at \(P\) on a faraway screen placed parallel to plane of the slit. The first diffraction minimum is formed at \(Q,\) as shown on the screen. Let \(C\) be a 'point' so that it divides the slit \(AB\) in the ratio \(\dfrac{AC}{CB}=\dfrac12,\) i.e. \(AC\) represents the upper \(\dfrac13^{rd}\) of the slit. The total amplitude of the oscillation arriving from \(AC\) at \(Q\) is \(A_1\) and from \(CB\) at \(Q\) is \(A_2\).
Then:
1. \(2 A_{1}=A_{2}\)
2. \(A_{1}=2 A_{2}\)
3. \(\sqrt{2} A_{1}=A_{2}\)
4. \(A_{1}=A_{2}\)
Then:
1. \(2 A_{1}=A_{2}\)
2. \(A_{1}=2 A_{2}\)
3. \(\sqrt{2} A_{1}=A_{2}\)
4. \(A_{1}=A_{2}\)
Subtopic: Â Diffraction |
Level 3: 35%-60%
Hints
Young's double-slit experiment is conducted with light of wavelength \(\lambda.\) The double-slit is shifted towards the source by a distance \(L,\) and the position of the \(5^{\text{th}}\) fringe is shifted by:
| 1. | \(\dfrac{5\lambda D}{d}\) | 2. | \(\dfrac{5\lambda L}{d}\) |
| 3. | \(\dfrac{5\lambda (L+D)}{d}\) | 4. | \(\dfrac{5\lambda (L-D)}{d}\) |
Subtopic: Â Young's Double Slit Experiment |
Level 3: 35%-60%
Hints
Consider sunlight incident on a pinhole of width \(10^{3}~\mathring{{A}}\). The image of the pinhole seen on a screen shall be:
| (a) | a sharp white ring |
| (b) | different from a geometrical image |
| (c) | a diffused central spot, white in colour |
| (d) | diffused coloured region around a sharp central white spot |
Choose the correct option from the given ones:
| 1. | (a) and (c) only |
| 2. | (a) and (d) only |
| 3. | (b) and (d) only |
| 4. | (b) and (c) only |
Subtopic: Â Diffraction |
Level 3: 35%-60%
Hints
Consider a parallel beam of monochromatic light of wavelength \(600~\text{nm}.\) It is allowed to pass through a slit of width \(0.15~\text{mm}.\) Assume that the angles involved are very small. The angular divergence in which most of the light gets diffracted will be:
1. \(4\times 10^{-3}~\text{rad}\)
2. \(2.0\times10^{-3}~\text{rad}\)
3. \(8.0\times10^{-3}~\text{rad}\)
4. \(90^\circ\)
1. \(4\times 10^{-3}~\text{rad}\)
2. \(2.0\times10^{-3}~\text{rad}\)
3. \(8.0\times10^{-3}~\text{rad}\)
4. \(90^\circ\)
Subtopic: Â Diffraction |
Level 3: 35%-60%
Hints
Polarized light incident on a polaroid. Let \(I_{0}\)
| 1. | Zero | 2. | \(\dfrac{I_{0}}{2}\) |
| 3. | \(I_{0}\) | 4. | \(\dfrac{I_{0}}{N}\) |
Subtopic: Â Polarization of Light |
Level 3: 35%-60%
Hints
Young's double-slit experiment is conducted with light of an unknown wavelength, the waves arriving at the central point on the screen are found to have a phase difference of \(\dfrac{\pi}{2}.\) The closest maximum to the central point is formed behind one of the slits. The separation between the slits is \(d,\) and the slit to screen separation is \(D.\) The longest wavelength for this to happen is:
| 1. | \(\dfrac{2d^2}{D}\) | 2. | \(\dfrac{2d^2}{3D}\) |
| 3. | \(\dfrac{d^2}{2D}\) | 4. | \(\dfrac{d^2}{6D}\) |
Subtopic: Â Young's Double Slit Experiment |
Level 3: 35%-60%
Hints
Sound waves travel faster in water than in air. Imagine a plane sound wavefront incident at an angle \(\alpha\) at the air-water interface; the refracted wavefront making an angle \(\beta\) with the interface. Then,
| 1. | \(\alpha>\beta\) |
| 2. | \(\beta>\alpha\) |
| 3. | \(\alpha=\beta\) |
| 4. | the relation between \(\alpha~\&~\beta \) cannot be predicted. |
Subtopic: Â Huygens' Principle |
Level 3: 35%-60%
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