Question

Which of the following is incorrect ray diagram for thin concave lens:
A)

B)

C)

D) All are incorrect

Answer 1

Hint
We know that a concave lens has diverging nature means it diverges all the rays after passing through it. A ray is diverged, if angle between the ray and principal axis is increased or the rays are bent away from the principal axis after passing through the lens.

Complete step by step solution
The figure in option (A) shows a ray coming parallel to the principal axis and bent away from the principal axis means it is diverged after passing through the concave lens, that this is the correct ray diagram.
In the figure in option (B), we can see that ray bends toward the principal axis means that ray converge after passing through lens and this is not possible with concave lens because concave lens only diverges the rays never converge them, than this ray diagram is incorrect.
And in figure in option (C), rays diverge by lens as it bends away from the principal axis after passing through the concave lens, then this ray diagram is correct.
Then there is only one incorrect ray diagram that is option (B).
Hence the correct answer is option (B).

Note The ray diagram shown in option (B) is correct for a convex lens because a convex lens converges the rays after passing through it. But if we place the given concave mirror in liquid of high refractive index thar glass then the concave mirror starts behaving like a convex lens and in this condition Option (B) is the correct diagram but option A and C are incorrect diagrams.