A thin symmetric convex lens of focal length is placed in air

PHYSICS · Subjective · AP · Physics 2: Algebra-based · Geometric Optics · Geometric Optics

Problem

A thin symmetric convex lens of focal length

f

is placed in air. (a) Sketch a neat ray diagram for an object at a distance

u

on the left of the optical centre

O

of the lens. Mark the image point

I

at distance

v

on the right. (b) From the geometry of the diagram and without assuming any known formula, derive the relation

\frac{1}{v}-\frac{1}{u}=\frac{1}{f}.

30\,\text{cm}

in front of a convex lens of focal length

20\,\text{cm}

. Using the result of part (b), calculate the position and nature of the image and determine the linear magnification.