Question

5. If two plane mirrors are inclined at an angle of 120˚ to each other, how many images of an object are formed?​

Answer 1

Formula :

$\frac{360}{given \: angle \: } - 1$

Solution :

$\frac{360}{120} - 1 \\ 3 - 1 = 2$

Answer :

2 images of an object are formed.

hope it helps...

Answer 2

★ Provided Question ★

5. If two plane mirrors are inclined at an angle of 120˚ to each other, how many images of an object are formed?

★ Required Answer ★

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

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.

Note:

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

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

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

In this question we are given that the two plane mirrors are inclined at 120° to each other i.e the angle between the mirrors. So let's solve this by the formula given above:

We know that,

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

Where,

• Number of images formed = ?
• $\theta$ (angle between the mirrors)= 120°

Substituting values:

$\rm { No. \: of \: images = \dfrac{360°}{\theta} -1 }$

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$\rm { No. \: of \: images = \dfrac{360°}{120°} -1 }$

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$\rm { No. \: of \: images = 3-1 }$

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$\rm { No. \: of \: images = 2 }$ $\red { \bigstar }$

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Thus, 2 images of an object are formed when two plane mirrors are inclined at an angle of 120˚ to each other.

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