Write a short note on power of lens
Answers
Explanation:
power of lens is the ability of the lens to converge the rays of light falling on it. it can also be defined as p=1/f where f is the focal length. power of a lens is the reciprocal of its focal length. dioptre is the s.i unit of power of lens.
Answer:
Power of a lens is defined as the inverse of focal length (in meters) of the lens. It is a measure of the amount of deviation of light ray produced by a lens, more the power, more is the deviation. Unit of power is Dioptre (D).
P=f1
Note:
Convex lens has positive power and concave lens has negative power.
Power of a plane glass plate is 0.
Power of combinations of lenses kept close to each other is equal to the sum of individual powers of each lens.
Magnification is 0.5 when the object distance is 10 cm. Find the power of the concave lens :
m=uv=0.5
m=uv=0.510v=0.5
m=uv=0.510v=0.5v=5cm
m=uv=0.510v=0.5v=5cmNow using:
m=uv=0.510v=0.5v=5cmNow using:v1−u1=f1
m=uv=0.510v=0.5v=5cmNow using:v1−u1=f1−51−−101=f1
m=uv=0.510v=0.5v=5cmNow using:v1−u1=f1−51−−101=f1f=−10cm
m=uv=0.510v=0.5v=5cmNow using:v1−u1=f1−51−−101=f1f=−10cmp=−10100 D
m=uv=0.510v=0.5v=5cmNow using:v1−u1=f1−51−−101=f1f=−10cmp=−10100 D=−10D