HC Verma Chapter 18 Problem 14 – Object at focal point

Given

u=-15 cm = -f for f=15 cm lens

Find

Image location

Formula

1/v = 1/f + 1/u = 1/15 – 1/15 = 0

Solution

v = infinity

Answer

Image at infinity; rays emerge parallel

Diagram / Concept

Used in collimators and projectors

Notes

Magnification undefined (infinite image size)