In a laboratory demonstration

PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Geometric Optics · Geometric Optics

Problem

In a laboratory demonstration, a thin converging lens is used to project a sharp real image of a candle onto a screen that is fixed

45\,\text{cm}

on the opposite side of the lens from the candle. Symbolically denote the object distance by

s_{o}

, the image distance by

s_{i}

, and the focal length by

f

. (1) Derive an algebraic expression for

s_{o}

in terms of

s_{i}

and

f

. Do not substitute numerical values in this part. (2) Using the expression from part (a), determine

s_{o}

when

f = 12\,\text{cm}

and

s_{i}=45\,\text{cm}

. (3) From your algebraic result in part (a), state the condition on

s_{o}

relative to

f

that must be satisfied in order for the lens to form a real image on the screen. Justify your statement with reference to the derived equation.