4.1 – Verifying the Lens Equation (Leaving Cert Physics): Flashcards

$\frac{1}{f} = \frac{1}{u} + \frac{1}{v}$

Focal length of the lens

Object distance (object to lens)

Image distance (lens to image)

Object distance $u$ must be greater than focal length $f$

Focus lens on distant object, measure image to lens distance

At least 5 (some magnified, some diminished images)

Calculate $f$ for each trial, find average, compare to known $f$

Plot $\frac{1}{u}$ vs $\frac{1}{v}$, check for straight line

Both intercepts equal $\frac{1}{f}$

Straight line with negative slope

Affects accuracy of measuring $v$ (image distance)

Introduces error in both $u$ and $v$ measurements

Reading metre stick from inconsistent angles (systematic if always same wrong angle, random if varying)

Object distance $u$ is less than focal length $f$