Question

A boy with a 10cm long stick is standing 2m away from a plane mirror. How long is the image of the stick?
A) 40 cm
B) 20 cm
C) 5 cm
D) 10 cm

Answer 1

After listing the properties of the plane mirror, we can check how the image of an object will be seen in it.

Complete step by step answer:
Properties of the image formed in a plane mirror:
i) It is virtual: Cannot be obtained on screen, not real
ii) It is erect: Straight or upright
iii) The same size as that of the object
iv) Distance of object from mirror = Distance of image from the mirror
v) It is laterally inverted: Left appears right and vice-versa
Now,
According to the question:
The object is the stick; 10 cm long
Distance from the mirror = 2 m
From property iii) mentioned here about the image of the plane mirror,
Length of stick = 10 cm [As, Size of image = size of object]
Therefore, the length of the image of the stick is 10 cm and the correct option is D)
Diagrammatically:

Note: The surface of mirrors are polished so that they can reflect maximum light falling upon them.
We require at least two rays (shown through arrows in the figure) from an object to form an image.
In the case of the real image, the rays of light actually meet after reflection, and the image is obtained on the screen while in a virtual image, the rays just appear to meet (not actually meet) and cannot be obtained on the screen.
The phenomenon rays may undergo when falls on the surface are:
Reflection, refraction, and absorption.