]]>
LearnNext
Get a free home demo of LearnNext

Available for CBSE, ICSE and State Board syllabus.
Call our LearnNext Expert on 1800 419 1234 (tollfree)
OR submit details below for a call back

clear

Spherical Mirror

1,76,671 Views
Have a doubt? Clear it now.
live_help Have a doubt, Ask our Expert Ask Now
format_list_bulleted Take this Lesson Test Start Test

Spherical Mirror - Lesson Summary

Mirrors are the basic means of viewing our own beauty. There are two types of mirrors – plane mirrors and curved mirrors. If the curved mirror is a part of a huge sphere, then the mirror is a spherical mirror. Spherical mirrors can be further classified into two types – concave mirrors and convex mirrors.  Like plane mirrors, spherical mirrors also follow the laws of reflection. 

Terms Associated with Spherical Mirrors

     •  Centre of curvature (C) is the centre of the sphere, of which the mirror is a part.
     •  Radius of curvature (R) is the radius of the sphere, of which the mirror is a part.
     •  Pole (P) is the geometric centre of the spherical mirror.
     •  Principal axis is the line joining the pole and the centre of curvature.
     •  Principal focus (F) is the point on the principal axis, where a parallel beam of light, parallel to the principal axis after reflection converges in the case of a concave mirror and appears to diverge from in the case of a convex mirror.
     •  Focal length (f) is the distance of the principal focus from the pole of the mirror.

There are two types of images: real and virtual. Real images are those that can be caught on a screen while virtual images are those that cannot be caught on a screen.

Concave Mirror

If a part of a hollow glass sphere is cut and the cut part of the sphere is coated outside with silver or similar material, then its inner surface reflects the entire light incident on it, and thus, forms a mirror. Since the inner surface is a concave surface, the mirror so formed is called a concave mirror.

Concave mirrors converge the light incident on them and hence are called converging mirrors. You can observe yourself magnified when the mirror is placed close to your face. This is due the position of the object between the focus and the pole. As the object moves away from the mirror, the size of its image reduces along with its distance from the mirror. If an object is placed close to a concave mirror such that the distance between the mirror and the object is less than its focal length, then a magnified and virtual image is formed. Due to this property, concave mirrors are used as shaving mirrors, and by dentists to view clearly the inner parts of the mouth.

Convex Mirror

If the cut part of the glass sphere is coated from inside with silver or a similar material, then its outer surface reflects the entire light incident on it, and thus forms a mirror. Since the outer surface is a convex surface, the mirror so formed is called a convex mirror.

Convex mirrors diverge the light incident on them and hence they are called the diverging mirrors. Due to this they always form diminished, virtual and erect images irrespective of the position of the object in front of them. Thus, the magnification produced by these mirrors is always less than one. The field of view for a convex mirror is greater than that for a plane mirror, the aperture being the same. Hence, convex mirrors are used as rear-view mirrors in vehicles. It is also installed behind automated teller machines as a security measure. 

Mirror Formula and Sign Conventions 

The relation between the focal length (f), object distance (u) and the image distance (v) is given by 1 f = 1 u + 1 v . This is called the mirror formula.

All the distances are measured from the pole of the mirror. If we measure the distances in the direction of the incident light, then they are taken positive or else they are taken negative. These constitute the sign conventions.

Comments(0)

Feel the LearnNext Experience on App

Download app, watch sample animated video lessons and get a free trial.

Desktop Download Now
Tablet
Mobile
Try LearnNext at home

Get a free home demo. Book an appointment now!

GET DEMO AT HOME