Q. No.
A mark on the surface of the sphere \(\left(\mu= \frac{3}{2}\right)\) is viewed from a diametrically opposite position. It appears to be at a distance \(15~\text{cm}\) from its actual position. The radius of the sphere is:
1. \(15~\text{cm}\)
2. \(5~\text{cm}\)
3. \(7.5~\text{cm}\)
4. \(2.5~\text{cm}\)
1. \(15~\text{cm}\)
2. \(5~\text{cm}\)
3. \(7.5~\text{cm}\)
4. \(2.5~\text{cm}\)
A light ray from the air is incident (as shown in the figure) at one end of glass fibre (refractive index \(\mu= 1.5\)) making an incidence angle of \(60^{\circ}\) on the lateral surface so that it undergoes a total internal reflection. How much time would it take to traverse the straight fibre of a length of \(1\) km?
1. \(3.33~\mu\text{s}\)
2. \(6.67~\mu\text{s}\)
3. \(5.77~\mu\text{s}\)
4. \(3.85~\mu\text{s}\)
If there had been one eye of a man, then:
| 1. | image of the object would have been inverted |
| 2. | visible region would have decreased |
| 3. | image would have not been seen in three dimensional |
| 4. | Both (2) and (3) |
The near point of a person is \(50~\text{cm}\) and the far point is \(1.5~\text{m}.\) The spectacles required for reading purposes and for seeing distant objects are respectively:
| 1. | \(+2\text{D}, -\frac{2}{3}~\text{D}\) |
| 2. | \( +\frac{2}{3}~\text{D},-2\text{D}\) |
| 3. | \(-2\text{D}, -\frac{2}{3}~\text{D}\) |
| 4. | \( -\frac{2}{3}~\text{D},+2\text{D}\) |
An astronomical refracting telescope will have large angular magnification and high angular resolution when it has an objective lens of:
| 1. | Small focal length and large diameter |
| 2. | Large focal length and small diameter |
| 3. | Large focal length and large diameter |
| 4. | Small focal length and small diameter |
| 1. | \(8\) | 2. | \(10\) |
| 3. | \(12\) | 4. | \(16\) |
If the focal length of the objective lens is increased, then magnifying power of:
| 1. | microscope will increase but that of telescope decrease |
| 2. | microscope and telescope both will increase |
| 3. | microscope and telescope both will decrease |
| 4. | microscope will decrease but that of the telescope will increase |
| 1. | \(\mu A \) | 2. | \(\frac{\mu A}{2} \) |
| 3. | \(A / \mu \) | 4. | \(A / 2 \mu\) |
A concave mirror of the focal length \(f_1\) is placed at a distance of \(d\) from a convex lens of focal length \(f_2\). A beam of light coming from infinity and falling on this convex lens-concave mirror combination returns to infinity. The distance \(d\) must be equal to:
1. \(f_1 +f_2\)
2. \(-f_1 +f_2\)
3. \(2f_1 +f_2\)
4. \(-2f_1 +f_2\)
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