Practice portal › Ray Optics and Optical Instruments › Reflection by Plane and Spherical Mirrors
Asked in GSEB Board July 2022 · Mirror formula and magnification
Given: a concave mirror with the object between the pole and the focus.
Idea: write f = -f₀ and u = -u₀ with u₀ < f₀, and let the mirror formula say what happens.
1/v = 1/f-1/u = -1/(f₀)+1/(u₀) = (f₀-u₀)/(u₀ f₀), which is positive because u₀ < f₀.
A positive v puts the image behind the mirror, where no light actually reaches, so the image is virtual.
The magnification is m = f/(f-u) = (f₀)/(f₀-u₀), which is positive and greater than 1: erect and enlarged.
This is the shaving-mirror case -- hold your face inside the focus of a concave mirror and you see an upright, magnified image behind the glass.
Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.
Practise this with a timer