Prove, in the case of a convex mirror, that 1 v - 1 u = 2 r = 1 f .

Let AB be an object lying on the principle axis of the convex mirror of small aperture. Virtual image is behind the mirror A'B'. Draw LN perpendicular to the principle axis. Now ∆ NLF and A'B'F are similar. Therefore, A ' B ' N L = A ' F N F Since aperture is small, point N lies very close to P. So, N F = P F , L N = A B Also, ∆ ABC and A'B'C are similar, so, A ' B ' A B = A ' C A C = P C - P A ' P A + P C So we get, P F - P A ' P F = P C - P A ' P A + P C . . . . . . ( i ) From diagram, P A ' = v P F = f P C = R = 2 f P A = u (without any sign convention) So, equation (i) becomes, f - v f = 2 f - v u + 2 f ⇒ 2 f 2 - v f = u f - u v + 2 f 2 - 2 v f ⇒ u v = u f - v f Dividing by u v f , we get, 1 f = 1 v - 1 u .

E M B I B E

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 6

MEDIUM

12th West Bengal Board

IMPORTANT

Earn 100

Two plane mirrors are at right angles to each other. A ray of light is reflected successively by the Mirrors. Show that the incident ray and final emergent ray are parallel to each other.

Important Questions on Reflection of Light

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 7

Prove, with the help of a diagram, that a mirror of minimum length must be hung at a definite position in the wall in order that a man can see his full image.

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 8

A man stands at the centre of a room. A plane mirror hangs on the wall in front of him. Show that the minimum height of the mirror through which the man can see the full image of the wall behind him is one-third the height of the wall.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 9

Explain, with the help of a diagram, the action of periscopes. For what purpose is it used ?

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 10

Prove, in the case of a convex mirror, that

\frac{1}{v} - \frac{1}{u} = \frac{2}{r} = \frac{1}{f}

.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 11

Establish the relation connecting object distance, image distance and focal length of a spherical mirror. Show that the ratio of the length of the image formed by a concave mirror to the length of the object is equal to the ratio of their respective distances from the mirror.

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 12

Explain with neat diagram the formation of image of an extended object by reflection from a convex mirror. Obtain a relation between the object distance, image distance and the focal length of the mirror.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 13

How will you proceed to determine the focal length of a convex mirror ?

EASY

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 12 - Reflection of Light>EXERCISE 12>Q 1

An object P lies between two parallel plane mirrors