/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 4 An object is placed a symmetrica... [FREE SOLUTION] | 91Ó°ÊÓ

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An object is placed a symmetrically between two plane mirrors inclined at an angle of \(72^{\circ}\). The number of image formed is (a) 5 (b) 4 (c) 2 (d) infinite

Short Answer

Expert verified
(b) 4

Step by step solution

01

Understand the Concept of Number of Images Formed by Mirrors

To find the number of images formed by two plane mirrors inclined at an angle, we can use the formula: \[ n = \frac{360^{\circ}}{\theta} - 1 \]where \( \theta \) is the angle between the mirrors. This formula is applicable when the object is placed symmetrically between the mirrors.
02

Plug in the Given Angle into the Formula

Given that the angle \( \theta \) is \( 72^{\circ} \), substitute \( 72^{\circ} \) into the formula:\[ n = \frac{360^{\circ}}{72^{\circ}} - 1 \]
03

Calculate the Number of Images

Perform the calculation using the values:\[ n = \frac{360}{72} - 1 = 5 - 1 = 4 \]This calculation shows that 4 images are formed.
04

Interpret the Result

The calculation reveals that four images of the object are formed when it is placed symmetrically between two plane mirrors inclined at an angle of \(72^{\circ}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Number of Images
When two plane mirrors are positioned at an angle to each other, an interesting phenomenon occurs where multiple images of an object are created. This happens due to the repeated reflections between the two mirrors. To determine the number of images formed by inclined plane mirrors, a simple formula can be used:\[ n = \frac{360^{\circ}}{\theta} - 1 \]Here, \( n \) represents the number of distinct images formed and \( \theta \) is the angle between the mirrors.
  • The object must be placed symmetrically between the mirrors for the formula to be accurate.
  • This formula is very handy as it gives an immediate way to calculate how many images will appear without trial and error.
  • As an example, if the mirrors are at a \(90^{\circ}\) angle, you'll get exactly three images because \(\frac{360}{90} - 1 = 3\).
It’s fascinating to see how these simple calculations can predict such a visually complex setup! Keep this in mind next time you see two mirrors together—there’s some interesting math at work.
Mirror Reflection
Understanding how reflections work in mirrors is crucial, especially when dealing with more than one mirror. Plane mirrors, which are flat, reflect light in a predictable way. When light hits a mirror, it bounces back at the same angle:
  • The angle of incidence (the angle at which incoming light hits the mirror) is equal to the angle of reflection (the angle at which it bounces off).
  • This consistent behavior forms the basis of how images are reflected and observed.
  • Each reflection creates a virtual image which appears to be behind the mirror.
When two plane mirrors are involved, the reflected images can also simulate more depth and lead to multiple images. The principle of reflection is essential to predict and determine where an image will appear within the mirrors. By understanding these reflection principles, anyone can predict not just where an image will appear, but how many will form, based on the angles and positions involved.
Inclined Mirrors
Setting up two mirrors at an angle leads to the formation of multiple reflections, which is a staple concept in optical physics. Inclined mirrors can be found in common places like dressing rooms and telescopes. Here's what happens with inclined mirrors:
  • Positioning two mirrors at an angle allows you to see multiple facets of an object all at once.
  • The angle affects how many images of the object you will see.
  • If the angle is too small, the mirrors behave similarly to a circular mirror and can form a continuous pattern.
Inclined mirrors serve as a great educational demonstration of reflection and image formation.In the exercise scenario, the mirrors are at a \(72^{\circ}\) angle, resulting in the formation of four distinct images. This calculation follows directly from the relation between the angle of inclination and the number of images and can provide insightful learning for students exploring optics.When inclined mirrors are placed more creatively, they can also illustrate endless reflections through a visual effect, making them an excellent learning tool.

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Most popular questions from this chapter

A hypermetropie person has to use a lens of power \(+5 \mathrm{D}\) to normalise his vision. The near point of the hypermetropic eye is |al \(1 \mathrm{~m}\) (b) \(1.5 \mathrm{~m}\) (c) \(0.5 \mathrm{~m}\) (d) \(0.66 \mathrm{~m}\)

An object \(5 \mathrm{~cm}\) tall is placed \(1 \mathrm{~m}\) from a concave spherical mirror which has a radius of curvature of \(20 \mathrm{~cm}\). The size of the image is (a) \(0.11 \mathrm{~cm}\) (b) \(-0.55 \mathrm{~cm}\) (c) \(0.55 \mathrm{~cm}\) (d) \(0.60 \mathrm{~cm}\)

A ray of light from a denser medium strikes a rarer medium at angle of incidence \(\angle\) The reflected and refracted rays make an angle of \(90^{\circ}\) with each other. The angles of reflection and refraction are \(r\) and \(r^{\prime}\) respectively. The critical angle is (a) \(\sin ^{-1}\left(\tan r^{*}\right)\) (b) \(\sin ^{-1}(\tan r)\) (c) \(\tan ^{-1}\left(\tan t^{\prime}\right)\) (d) \(\tan ^{-1}(\tan i]\)

A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is (a) the focal points shifts away from the lens by a small distance (b) the focus remains undisturbed (c) the focus shifts to infinity (d) the focal points shifts towards the lens by a small distance

A car is moving with at a constant speed of \(60 \mathrm{kmh}^{-1}\) on a straight road. Looking at the rear view mirror, the driver finds that the car following him is at distance of \(100 \mathrm{~m}\) and is approaching with a speed of \(5 \mathrm{~km} \mathrm{~h}^{-1}\). In order to keep track of the car in the rear, the driver begins to glance alternatively at the rear and side mirror of his car after every \(2 \mathrm{~s}\) till the other car overtakes. If the two cars were maintaining their speeds, which of the following statement (s) is/are correct? (a) The speed of the car in the rear is \(65 \mathrm{~km} \mathrm{~h}^{-1}\) (b) In the side mirror the car in the rear would appear to approach with a speed of \(5 \mathrm{~km} \mathrm{~h}^{-1}\) to the driver of the leading car (c) In the rear view minor, the speed of the approaching car would appeat to decrease as the distance between the. cars decreases (d) In the side mirror, the speed of the approaching car would appear to increase as the distance between the cars decreases

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