A student tries to project a sharp image of a distant streetlamp onto a screen using…
PHYSICS · Single correct · CBSE · Physics · Light — Reflection and Refraction · Light — Reflection and Refraction
Problem
A student tries to project a sharp image of a distant streetlamp onto a screen using a single thin concave (diverging) lens but fails, no matter where the screen is placed. Which statement best explains why the desired real image cannot be formed with this lens alone?
(a) A concave lens can form a real image only if the object is placed closer than its focal length; because the streetlamp is effectively at infinity, no real image appears.
(b) A concave lens has a negative focal length that is so short the required screen position would be inside the glass itself.
(c) A concave lens causes parallel incident rays to diverge, so they never intersect to form a real image.
(d) Spherical aberration in concave lenses smears out any real image that might otherwise form.