Question

Assertion `:` The mirrorrs used in search lights are parabolic and not concave spherical.
Reason `:` In a concave spherical mirrorr the image formed is always virtual.
A. If both the assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer 1

Correct Answer - C
In search lights, we need an intense parallel beam of light. If a source is placed at the focus of a concave spherical mirrorr, only paraxial rays are rendered parallel. Due to large aperture of mirrorr, marginal rays give a divergent beam.
But in case of parabolic mirrorr, when source is at the focus, beam of light produced over the entire cross`-` section of the mirrorr is a parallel beam.