Question

Two plane mirrors a and b are placed at a distance 12 cm apart facing towards each other. An object is placed in between them at a distance 8 cm from the mirror

a. What will be the distance between the first two images formed in the mirror b

Answer 1

the image which is forming at B will at 4cm .then image will act as an object will form img2 at A at 16cm(12+4) .well then this will act as an object an new img3 will be formed at B at 28 cm

distace between two imgage at B =>28-4=24cm

Answer 2

Given that,

Two plane mirrors a and b are placed at a distance 12 cm apart facing towards each other.

An object is placed in between them at a distance 8 cm from the mirror a.

We know that,

The image distance will be equal to the distance of object in plane mirror.

We need to calculate the distance of the image in the mirror a

Using formula for image distance

$v_{a}=2u_{a}$

Put the value into the formula

$v_{a}=2\times8$

$v _{a}= 16\ cm$

We need to calculate the distance of the image in mirror b from the image in mirror a

Using formula for image distance

Distance of image in mirror b  =distance of image in mirror a + distance of image in mirror b

$v_{ab}=2u_{a}+2u_{b}$

Put the value into the formula

$v_{ab}=16+8$

$v_{ab} = 24\ cm$

We need to calculate the distance of the image in the mirror b

Using formula for image distance

$v_{b}=2u$

Put the value into the formula

$v_{b}=2\times4$

$v_{b} = 8\ cm$

We need to calculate the distance between the first two images formed in the mirror b

Using formula for distance of image

$v_{b}'=v_{ab}-v_{b}$

Put the value into the formula

$v_{b}'=24-8$

$v_{b}'=16\ cm$

Hence, The distance between the first two images formed in the mirror b is 16 cm.