Question

An object is placed 30 cm in front of Plano convex lens with its spherical surface of radius of curvature 20 cm. If the refractive index of the material of the lens is 1.5, find the position and nature of the image formed.​

Answer 1

Explanation:

u= -30

radius of curvature=20

focal length= R/2

= 20/2

=10

refractive index=1.5

1/v-1/u=1/f

1/v=1/f+1/u

1/v=1/10+1/-30

1/v=3+(1-)/30

1/v=2/30

v=+15

the image is real and inverted

Answer 2

Answer: using lens maker formula in plano convex lens the radius of curvature of plane mirror will be infinity and for convex part it will be +ve

R1 = convex lens part R2 = plane mirror

1/f = (refractive index-1) [1/R1 - 1/R2]

1/v - 1/u = (1.5-1) [1/20 - 1/infinity]

1/v - 1/-30 = 0.5 × 1/20 as 1/infinity will be zero

Therefore

1/v + 1/30 = 1/2 × 1/20 [0.5 = 1/2]

1/v = 1/40 - 1/30

V = -120cm

M = v/u = -120/-30 = +4

Virtual and erect

Explanation: