Which one of the following ray diagrams (for a concave/diverging lens) is correct?
The Correct Option is C
Solution and Explanation
Reasoning (Key ray rules for a concave lens):
- A ray
parallel to the principal axis after refraction appears to
diverge from the focus on the same side. - A ray directed
towards the focus on the incident side emerges
parallel to the principal axis. - A ray through the
optical centre goes
undeviated.
In option (C), the incident ray is aimed towards the lens’s near focus \(F\) (shown by a dashed extension); after refraction it emerges
parallel to the principal axis — exactly matching rule 2. Therefore, (C) is correct.
\[ \text{Concave lens: } \begin{cases} \text{towards } F \;\Rightarrow\; \text{emerges parallel},\\ \text{parallel} \;\Rightarrow\; \text{appears from } F. \end{cases} \]
Why others are wrong (brief): (B) makes a parallel ray pass through the far focus (that’s for a convex lens, not concave). (D) shows parallel rays remaining parallel after the lens (concave lens should diverge them). (A) does not satisfy any standard concave-lens rule as drawn.
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