REFLECTION AND MIRRORS

A man is 6.0 ft tall. What is the smallest size plane mirror he can use to see his entire image

• 3.0 ft

• 6.0 ft

• 12 ft

• 2.0 ft

Answer explanation

It does not matter how far you are from the mirror. In order to see full image of a person, the minimum size of the mirror should be one half the person's height. This is so because, in reflection, the angle of incidence is equal to angle of reflection. So, to see the image of a 6 ft tall person, a 3 ft long mirror is required.

Focal length of a plane mirror is

• Zero

• Infinite

• 5

• 25

Find the angle of incidence and angle of reflection from the diagram.

• 45^o, 40^o

• 60^o, 60^o

• 55^o, 55^o

• 30^o, 30^o

The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

• Between the principal focus and the centre of curvature

• At the centre of curvature

• Beyond the centre of curvature

• Between the pole of the mirror and its principal focus.

Answer explanation

The position of the object should be between the pole of the mirror and its principal focus.

No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be

• plane

• concave

• convex

• All of these

Name the mirrors shown in figure (a) and (b) :

• (a) and (b) both are convex mirror

• (a) and (b) both are concave mirror

• (a) is convex mirror

  (b) is concave mirror

• (a) is concave mirror

  (b) is convex mirror

What type of mirror is this?

• CONVEX

• CONCAVE

• PLANE

• BOTH CONVEX AND PLANE

A spherical mirror to be made from a cut portion of

• hollow sphere of metal

• solid sphere of glass

• hollow sphere of glass

• hollow sphere of glass

In order to determine focal length of a concave mirror by obtaining the image of distant object on screen, you need to measure the distance between

• mirror and the screen

• object and screen

• mirror and object

• mirror and screen also between object

Answer explanation

For an object at infinity, all the paraxial rays after reflection from the concave mirror will pass through the focus, thus the image is formed at focus. Hence the focal length of the concave mirror can be determined by measuring the distance between the screen and the mirror. 

An object is placed at a distance of 20 cm in front of concave mirror of focal length 10 cm. The image produced is

• real, inverted and diminished

• real, inverted and enlarged

• real, inverted and same size

• virtual, erect and enlarged