HC Verma Chapter 18 Problem 7 – Refraction at concave surface, glass to air

Given

Object in glass (n=1.5) 40 cm from concave surface R=-20 cm to air

Find

Image distance

Formula

n2/v – n1/u = (n2-n1)/R

Solution

1/v – 1.5/(-40) = (1-1.5)/(-20); 1/v + 0.0375 = 0.025; v = -80 cm

Answer

v = -80 cm (virtual)

Diagram / Concept

Ray from dense to rare medium; concave R is negative

Notes

Virtual image on same side as object