HC Verma Chapter 18 Problem 6 – Refraction at convex spherical surface

Given

Object 30 cm from convex surface R=20 cm, n1=1 to n2=1.5

Find

Image distance v

Formula

n2/v – n1/u = (n2-n1)/R

Solution

1.5/v – 1/(-30) = 0.5/20; 1.5/v = 0.025 – 0.0333 = -0.0083; v = -180 cm

Answer

v = -180 cm (virtual, same side as object)

Diagram / Concept

Single refracting surface formula with Cartesian signs

Notes

Negative v means virtual image on object side