Practice portal › Ray Optics and Optical Instruments › Reflection by Plane and Spherical Mirrors
Asked in GSEB Board July 2021 · Mirror formula and magnification
Given: the lower half of a concave mirror is made non-reflective.
Idea: every point of the object sends light to the whole mirror, and every point of the mirror sends some of it to the matching image point.
So the upper half alone still builds the complete image, in the same place and of the same size -- no part of the object goes missing.
What does change is how much light arrives: only half the reflecting area is left, so half the energy reaches the image.
Intensity is power spread over the image area, and that area is unchanged, so the intensity falls to half.
The image therefore stays whole and becomes half as bright.
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