Lenses — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Lenses MCQs with step-by-step solutions (8 questions). Part of Light & Optics. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Lenses · medium · theory
A convex lens is also called a converging lens because it:
A. spreads parallel rays apart
B. absorbs light
C. brings parallel rays of light together at a focus ✓ Correct
D. reflects light
Solution: A convex lens converges parallel rays to a real focus, unlike a concave (diverging) lens.
Q2 — Lenses · medium · theory
A magnifying glass (simple microscope) uses a:
A. plane mirror
B. convex lens ✓ Correct
C. convex mirror
D. concave lens
Solution: A convex lens held close to an object gives an enlarged, erect, virtual image — a magnifying glass.
Q3 — Lenses · medium · numerical
The power of a convex lens of focal length 0.5 m is:
A. −2 D
B. +2 D ✓ Correct
C. +0.5 D
D. +5 D
Solution: Power $= \dfrac{1}{f(\text{m})} = \dfrac{1}{0.5} = +2$ dioptre (positive for a convex lens).
Q4 — Lenses · hard · numerical
The power of a lens of focal length 25 cm is:
A. +4 D ✓ Correct
B. +2.5 D
C. +0.25 D
D. +25 D
Solution: $f = 25$ cm $= 0.25$ m, so power $= \dfrac{1}{0.25} = +4$ D.
Q5 — Lenses · hard · theory
A concave lens always forms an image that is:
A. real, inverted and magnified
B. virtual, erect and diminished ✓ Correct
C. real and erect
D. virtual and magnified
Solution: For all object positions, a concave (diverging) lens forms a virtual, erect, diminished image.
Q6 — Lenses · easy · theory
A convex lens is also known as a:
A. Cylindrical lens
B. Diverging lens
C. Plane lens
D. Converging lens ✓ Correct
Solution: A convex lens is thicker in the middle and brings parallel rays together at a focus, so it is called a converging lens. A concave lens spreads rays out and is the diverging lens.
Q7 — Lenses · medium · numerical
The power of a lens is +2 dioptre. What is its focal length?
A. 0.2 m
B. 2 m
C. 5 cm
D. 0.5 m ✓ Correct
Solution: Power P = 1/f, where f is in metres. So f = 1/P = 1/2 = 0.5 m (50 cm). The positive sign confirms it is a convex lens. Writing f = 2 m wrongly sets f equal to P.
Q8 — Lenses · hard · theory
An object is placed at 2F (twice the focal length) in front of a convex lens. The image formed is:
A. Real, inverted and the same size, at 2F on the other side ✓ Correct
B. Virtual, erect and magnified
C. Real, inverted and highly diminished
D. A single point image right at the focus
Solution: For a convex lens, an object at 2F gives a real, inverted image of the same size located at 2F on the far side. This mirrors the same-size rule and is the boundary between magnified and diminished images.