Q. No.A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power of a cut-lens will be
1. 2 D
2. 3 D
3. 4 D
4. 5 D
A symmetric double convex lens is cut in two equal parts by a plane containing the principal axis. If the power of the original lens was \(4~\text{D}\), the power of a divided lens will be:
1. \(2~\text{D}\)
2. \(3~\text{D}\)
3. \(4~\text{D}\)
4. \(5~\text{D}\)
Two concave lenses \(L_1\) and \(L_2\) are kept in contact with each other. If the space between the two lenses is filled with a material of smaller refractive index, the magnitude of the focal length of the combination:
| 1. | becomes undefined. |
| 2. | remains unchanged. |
| 3. | increases. |
| 4. | decreases. |
A thin lens is made with a material having refractive index \(\mu=1.5\). Both sides are convex. It is dipped in water (\(\mu=1.33\)). It will behave like:
1. a convergent lens
2. a divergent lens
3. a rectangular slab
4. a prism
A convex lens is made of a material having refractive index \(1.2.\) Both the surfaces of the lens are convex. If it is dipped into water (\(\mu=1.33\) ), it will behave like:
1. a convergent lens
2. a divergent lens
3. a rectangular slab
4. a prism
A point object O is placed on the principal axis of a convex lens of focal length f = 20 cm at a distance of 40 cm to the left of it. The diameter of the lens is 10 cm. An eye is placed 60 cm to right of the lens and a distance h below the principal axis. The maximum value of h to see the image is
1. 0
2. 2.5 cm
3. 5 cm
4. 10 cm
The rays of different colours fail to converge at a point after going through a converging lens. This defect is called:
1. spherical aberration
2. distortion
3. coma
4. chromatic aberration
If the light moving in a straight line bends by a small but fixed angle, it may be a case of
(a) reflection
(b) refraction
(c) diffraction
(d) dispersion
Choose the correct option:
| 1. | (a) and (b) |
| 2. | (b) and (c) |
| 3. | (c) and (d) |
| 4. | all of these |
Mark the correct options:
| 1. | if the incident rays are converging, we have a real object. |
| 2. | if the final rays are converging, we have a real image. |
| 3. | the image of a virtual object is called a virtual image. |
| 4. | if the image is virtual, the corresponding object is called a virtual object. |
Which of the following (referred to a spherical mirror) do (does) not depend on whether the rays are paraxial or not?
(a) pole
(b) focus
(c) radius of curvature
(d) principal axis
Choose the correct option:
1. (a) and (b)
2. (b) and (c)
3. (a), (b) and (c)
4. (a), (c) and (d)
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