Spherical Lens

Q. What is principal focus

Q.

A convex lens is held in water. What would be the change in the focal length? [2 MARKS]

Q. Which of the following is an appropriate condition for a thin lens?

1. Aperture >> Radius of curvature

2. Aperture = Radius of curvature

3. Aperture << Radius of curvature

4. Aperture is more than the focal length.

Q.

If AB = 10 cm & DB = 40 cm (diameter)

What is radius of curvature & focal length?

1. 40 cm, 10 cm

2. 20 cm, 20 cm

3. 40 cm, 5 cm

4. 20 cm, 10 cm

Q.

If AB = 10 cm & DB = 40 cm (diameter). What is the radius of curvature & focal length?

1. 20 cm, 20 cm

2. 40 cm, 5 cm

3. 20 cm, 10 cm

4. 40 cm, 10 cm

Q. In lenses, all the distances are measured from optical centre of the lens as a convention.

1. False
2. True

Q. Focal length of a lens is twice the radius of curvature.

1. True
2. False

Q.

Observe the optical systems above. Given that all surfaces are made of transparent glass and the dotted surfaces represent plane surface. Which among them can be considered as lenses?

1. I, II, IV, V

2. I, II, III, IV

3. I, II, III, V

4. I, IV only

Q. The distance between optical centre and is known as focal length of the lens.

1. principal focus
2. centre of curvature
3. aperture

Q. A ray from an object kept at some distance is incident on the lens as shown. Where is the image formed, if P'P is the principal axis and A is the focus?

1. at A
2. cannot be determined
3. forms at infinity
4. At C

Q. Lenses have two radii of curvature, as they have two refracting curved surfaces.

1. True
2. False

Q. A light ray passing through a spherical lens undergoes refractions.

1. two
2. one
3. four

Q. Principal axis of the lens is also called as vertical axis.

1. True
2. False

Q. Distance between focus and centre of curvature is equal to ___.

1. half of radius of curvature
2. radius of curvature
3. object distance
4. height of the mirror

Q.

In case of a lens, a light ray passes through ___ without undergoing any deviation.

1. focal length

2. optic centre

3. focus

4. centre of curvature