Consider a glass with a hollow sphere and a reflecting surface. This reflecting hollow surface of sphere of which either sides are polished, forms the spherical mirrors. Spherical Mirrors are of two types: (a) Concave Mirror Copy the link given below and paste it in new browser window to get more information on Reflection of Light by Spherical Mirrors www.askiitians.com/iit-jee-ray-optics/reflection-of-light-by-spherical-mirrors/

1. Reflection Of light by spherical
mirrors

2. Spherical mirrors
Spherical mirror: Consider a glass with a hollow sphere and a reflecting
surface. This reflecting hollow surface of sphere of which either sides are
polished, forms the spherical mirrors. Spherical mirrors are of two types:
Concave mirror and b) convex mirror.
The inward curved reflecting surface of the spherical mirror is known as
concave mirror and the outward curved reflecting surface of the same
spherical mirror is known a convex mirror.

3. Uses of concave and convex mirrors
Concave mirrors:
•Used as shaving and makeup mirrors
•Used as reflectors in search lights, projectors etc
• Used as mirrors by dentists
•Used in reflecting telescope
Convex mirrors:
• Used as rear view mirror
•Used as shaving and makeup mirrors
•Used as safety viewers at dangerous corners

4. Laws of reflection
The angle between the incident ray and normal i.e. angle of incidence is always
equal to the angle between normal and reflected ray i.e. angle of reflection
The ray which is incident on the surface, the normal and the ray which is
reflected back lies on the same plane.

5. Total Internal Reflection
• Total internal reflection: when a light travels from denser to
rarer medium then it gets refracted away from the normal. As
the angle of incidence is increased, the angle of refraction
also increases. A point comes when the angle of refraction is
90˚ and there is no further refraction . At this point, the
incident light gets totally reflected. This reflection is known as
Total internal reflection .

6. Sign convention
(a) When the light is travelling parallel to the principal axis, then the
reflected ray is supposed to pass through the focus of the mirror
(b) When the light travels through the centre of curvature, then it reflects
back and traces its original path that it travelled.
(c) When the light travels through the focus of the mirror, then the reflected
rays travels parallel to the principal axis.
It may be noted that these principles abide by the laws of reflection i.e. the
angle formed by the incident ray is equal to that angle formed by the
reflected ray.

7. Mirror equation and magnification
formula:
Mirror Equation: 1/f = 1/v + 1/u
Magnification formula (m) = -(v/u)
The mirror equation helps us to calculate the distance , location
and nature of the image formed at the mirror. The magnification
formula helps us to see if the image formed is magnified or
diminished. The mirror equation is derived using the standard sign
convention and in true for all cases

8. Conclusion
The formation of a image in concave mirror can be real or
virtual depending on the location and position of the object
placed away from the mirror. However, in case of convex
mirror , the image formed is always virtual. The formation of
image, be it in concave or convex mirror always abides by the
law of reflection.

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