Geometrical OpticsHard
Question
In the displacement method, a convex lens is placed in between an object and a screen. If one of the magnification is 3 and the displacement of the lens between the two positive is 24 cm, then the focal length of the lens is : -
Options
A.10 cm
B.9 cm
C.6 cm
D.16/3 cm
Solution
X = u2 - u1 = 24
m =
= 3 ⇒ v1 = 3u1 or u2 = 3u1
3u1 - u1 = 24 ⇒ u1 = 12 cm
Distance between object & screen is
D = v1 + u1 = 3u1 + u1 = 4 × 12 = 48 cm
Hence f =
=
= 9 cm
m =
= 3 ⇒ v1 = 3u1 or u2 = 3u13u1 - u1 = 24 ⇒ u1 = 12 cm
Distance between object & screen is
D = v1 + u1 = 3u1 + u1 = 4 × 12 = 48 cm
Hence f =
=
= 9 cmCreate a free account to view solution
View Solution FreeMore Geometrical Optics Questions
A telescope consisting of objective of focal length 60 cm and a single lens eye piece of focal length 5cm is focussed at...White light is passed through a prism of angle 5o If the refractive indices for red and blue colour are 1.641 and 1.659 ...A ray of light travelling in a transparent medium of refractive index μ, falls on a surfaces parting the medium fro...An astronomical telescope has focal lengths 100 & 10cm of objective and eyepiece lens respectively when final image is f...Two mirrors are inclined at an angle as shown in the figure. light ray is parallel to one of the mirrors. The ray will s...