Question

Find the number of images formed

by an object placed between the

two plane mirrors , when the

mirrors are inclined to each other at

(i) 72° (ii) 60°​

Answer 1

Explanation:

FORMULA=

$360 \div angle \: between \: mirrors - 1$

(I) - Angle =72 deg.

Number of images =

$360 \div 72 - 1$

$= 5 - 1$

=4 images.

(ii) - Number of images=

$360 \div 60 - 1$

$= 6 - 1$

=5 images.

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Answer 2

Required Answer:

Firstly let's understand the concept and review the formula to solve this question, so that we can solve it easily.

$\boxed { \large \bf \red { Concept : }}$

Here, the concept of multiple reflections has been used. To calculate the number of images of an object placed between two mirrors can be found from the formula:

$\boxed { \sf \pink { No. \: of \: images \: formed = \dfrac{360°}{\theta} -1 }}$

Where,

• $\theta$ is the angle between the mirrors.

$\boxed { \large \bf \red { Solution : }}$

(i) 72°

We know that,

• $\boxed { \sf \pink { No. \: of \: images \: formed = \dfrac{360°}{\theta} -1 }}$

$\sf { \longmapsto No. \: of \: images \: formed = \dfrac{360°}{72°} -1 }$

$\sf { \longmapsto No. \: of \: images \: formed = 5 -1 }$

$\longmapsto$ $\large{\underline{\textsf{\textbf{\purple{ 4 \: images }}}}}$

(ii) 60°

We know that,

• $\boxed { \sf \pink { No. \: of \: images \: formed = \dfrac{360°}{\theta} -1 }}$

$\sf { \longmapsto No. \: of \: images \: formed = \dfrac{360°}{60°} -1 }$

$\sf { \longmapsto No. \: of \: images \: formed = 6-1 }$

$\longmapsto$ $\large{\underline{\textsf{\textbf{\purple{ 5 \: images }}}}}$

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Note:

$\longmapsto$ The number of images formed by the two plane mirrors increases when the angle between the two mirrors decreases.

$\longmapsto$ When the angle between two mirrors are parallel to each other, infinite images are formed.

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