Question:

An object is placed Infront of a plane mirror 12 cm away from it. The object is kept fixed while the plane mirror is shifted towards the object by a distance of 4 cm. The length of shift in the position of image is equal to ___________ cm.

Updated On: Nov 29, 2024
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When an object is placed in front of a plane mirror, the image formed is at the same distance behind the mirror as the object is in front of it. Therefore, the distance between the object and the image is twice the distance between the object and the mirror.
Initially, the object is placed 12 cm away from the mirror. Therefore, the distance between the object and the image is 2 x 12 = 24 cm.
When the mirror is shifted towards the object by 4 cm, the distance between the object and the mirror becomes 12 - 4 = 8 cm. Therefore, the
distance between the object and the image becomes 2 x 8 = 16 cm.
The shift in the position of the image is the difference between the initial and final distances between the object and the image. Therefore, the shift in the position of the image is:
24 - 16 = 8 cm
So the length of the shift in the position of the image is 8 cm.
Answer. 8 cm
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Concepts Used:

Ray Optics and Optical Instruments

Optics, deals with the determination of behaviour and the properties of light, along with its interactions with the matter and also with the instruments that are used to detect it.

Ray optics is also known as the geometrical optics and it is a branch of science which describes light propagation.

Reflection is the change in direction of light at an interface in-between two different media so that the wave-front returns into a medium from which it was originated.

Speed of light is the rate at which the light travels in free space.

A phenomenal change in image formed when the light is passed from one medium to another which is called Refraction.

Total Internal Reflection is the reflection of light when the light ray enters into a rarer medium from a denser medium and the angle of incidence is higher than the critical angle of incidence then that light ray will be reflected back to the denser medium.

Read More: Ray Optics and Optical Instruments