A ray of light falls on a concave lens. It is aimed at the focus on the other side of the lens. After refraction, the ray
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → emerges parallel to the principal axis
A concave lens is a diverging lens. It bends a ray away from the principal axis. The focus on the other side of the lens is called its second focal point.
Option (1) passes through the focus on the side of the incoming light — Incorrect. This focus lies on the side from which the light comes. A ray that has passed through the lens cannot come back to that side.
Option (2) goes on without any deviation — Incorrect. Only a ray through the optical centre goes on without deviation. This ray strikes the lens away from the centre and is bent.
Option (3) appears to come from the focus on the other side — Incorrect. The focus on the other side lies ahead of the refracted ray. A ray moving away from the lens cannot appear to come from a point ahead of it.
Option (4) emerges parallel to the principal axis — Correct. The ray was heading for the second focal point. The lens bends it outwards, so it comes out parallel to the axis.
NCERT (2026-27):
Refraction by a lens – “(b) A ray of light incident on a concave lens appearing to meet the principal axis at second focus point emerges parallel to the principal axis after refraction …”