JAMB Physics 2016 Paper

Concept:Angular magnification of a telescope measures how much larger an object appears when viewed through the instrument compared with the unaided eye. For normal adjustment, it depends only on the focal lengths of the two lenses.Explanation:In a simple refracting telescope, the objective lens has a long focal length and the eyepiece has a short focal length.The angular magnification is given by $M = \frac{f_o}{f_e}$.Substituting $f_o = 30\ \mathrm{cm}$ and $f_e = 3\ \mathrm{cm}$: $M = \frac{30}{3} = 10$.The units cancel because both focal lengths are in centimetres, so $M$ is a pure number.This matches option B.Answer:$M = 10$, so the correct option is B.