Q. No.In normal adjustment, the angular magnification of an astronomical telescope is 39. If length of the tube is 2 m, then focal length of the objective and eyepiece are respectively:
1. 195 cm, 5 cm
2. 190 cm, 10 cm
3. 20 cm, 180 cm
4. 10 cm, 190 cm
A ray of light is incident on an equilateral prism at an angle of incidence i such that it is incident normally on other refracting faces. Find 'i'. [Take glass =2]
1. \(30^{\circ}\)
2. \(45^{\circ}\)
3. \(60^{\circ}\)
4. Not possible
The ratio of the velocity of light in a medium to the velocity of light in a vacuum is \(\frac{4}{5}\). If the ray of light is emerging from this medium into the air, then the critical angle for this interface of medium and air will be:
| 1. | \(30^\circ\) | 2. | \(37^\circ\) |
| 3. | \(53^\circ\) | 4. | \(45^\circ\) |
If a light ray is incident normally on face AB of a prism, then for no emergent ray from second face AC:
[refractive index of glass of prism]
| 1. | \(\mu=\frac{2}{\sqrt{3}}\) | 2. | \(\mu>\frac{2}{\sqrt{3}}\) |
| 3. | \(\mu<\frac{2}{\sqrt{3}}\) | 4. | μ can have any value. |
In a glass ( = 1.5) sphere with a radius of 10 cm, there is an air bubble B at a distance of 5 cm from C. The distance of the bubble from the surface of the sphere (i.e., point A) as observed from point P in the air will be:
| 1. | 4.5 cm | 2. | 20.0cm |
| 3. | 9.37 cm | 4. | 6.67 cm |
A lens forms an image of a point object placed at distance 20 cm from it. The image is formed just in front of the object at a distance 4 cm from the object (and towards the lens). The power of the lens is:
1. 2.25 D
2. 1.75 D
3. 1.25 D
4. 1.4 D
The distance between the object and its real image formed by a concave mirror is minimum when the distance of the object from the centre of curvature of the mirror is: [f focal length of the mirror]
1. Zero
2.
3. f
4. 2f
A point object O is placed at a distance 20 cm from a biconvex lens of the radius of curvature 20 cm and \(\mu=1.5.\) The final image produced by lens and mirror combination will be at:
| 1. | 10 cm from the mirror |
| 2. | 20 cm from the lens |
| 3. | - 20 cm from the lens |
| 4. | -15 cm from the mirror |
A person can see objects clearly between 1 m and 3 m. The power of lens required to correct near point will be:
1. 2.5 D
2. + 3 D
3. + 1.5 D
4. 1.75 D
In the case of a compound microscope, the image formed by the objective lens is:
| 1. | Virtual, erect, and diminished. |
| 2. | Real, erect, and magnified. |
| 3. | Virtual, inverted, and enlarged. |
| 4. | Real, inverted, and enlarged. |
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