Q. No.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. \(5~\text{D}\)
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)
The image of an extended object, placed perpendicular to the principal axis of a mirror, will be erect if
(a) the object and the image are both real
(b) the object and the image are both virtual
(c) the object is real but the image is virtual
(d) the object is virtual but the image is real
Choose the correct option:
1. (a) and (b)
2. (b) and (c)
3. (c) and (d)
4. (a) and (d)
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