1. Focal length of a plane mirror is ?

half of its aperture

double of its aperture

zero

infinity

Answer: zero

Explanation:


2. A concave mirror is a part of a sphere of radius 30cm. It’s focal length is ?

15cm

60cm

10cm

at infinity

Answer: 10cm

Explanation:


3. An object at a distance of + 15 cm is slowly moved towards the pole of a convex mirror. The image will get ?

enlarge and virtual

diminished and virtual

enlarged and real

shortened and real

Answer: diminished and virtual

Explanation:


4. A ray of light is travelling from a rarer medium to a denser medium. While entering the denser medium at the point of incidence, it ?

does not enter at all

bends away from the normal

bends towards the normal

goes straight into the second medium

Answer: bends towards the normal

Explanation:


5. Light from the Sun falling on a convex lens will converge at a point called ?

optical centre

radius of curvature

centre of curvature

focus

Answer: focus

Explanation:

The parallel ray coming from the sun, after refraction through the convex lens converge at its focus.


6. As light travels from a rarer to a denser medium it will have ?

increased velocity

decreased wavelength

decreased velocity

both (b) and (c)

Answer: both (b) and (c)

Explanation:

When light ray travel from rarer to denser medium, its velocity and wavelength both decrease as v = v?.


7. An object is placed at a distance of 0.25 m in front of a plane mirror. The distance between the object and image will be ?

0.5 m

0.125 m

1.0 m

0.25 m

Answer: 0.5 m

Explanation:

Distance between object and image = 0.25 + 0.25 = 0.5 m


8. An object is placed 20 cm in front of a plane mirror. the mirror is moved 2 cm towards the object. the distance between the positions of the original and final images seen in the mirror is ?

22 cm

10 cm

4 cm

2 cm

Answer: 4 cm

Explanation:

Distance between original image and final image = distance the mirror moved + same distance the image move= 2 + 2 = 4cm.


9. Under which of the following conditions a concave mirror can form an image larger than the actual object ?

When object is placed between the focus and centre of curvature

When object is kept at a distance greater than its radius of curvature

When object is kept at a distance less than its focal length

When the object is kept at a distance equal to its radius of curvature

Answer: When object is placed between the focus and centre of curvature

Explanation:


10. To obtain parallel ray from a point light source we use ?

both concave lens and convex mirror

both concave lens and concave mirror

both convex lens and concave mirror

both convex lens and convex mirror

Answer: both convex lens and concave mirror

Explanation: