Lenses — Practice Quiz
Kerala Board · Class 10 · Physics
Try a 4-question quiz on Lenses for Kerala Board Class 10 Physics: tap an answer to check it and see why. 44 questions in the full chapter test.
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Quick Quiz: Lenses
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A convex lens has a focal length of 20 cm. An object is placed 30 cm from the lens. Calculate the image distance using the lens equation.
The power of a lens with focal length 25 cm is:
When an object is placed between F and 2F of a convex lens, the image formed is:
A concave lens of focal length 15 cm forms an image of an object placed 20 cm away. Calculate the magnification.
Sample Questions
Which of the following are characteristics of a convex lens?
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Thicker at the center, Can converge light rays, Can form real images
A convex lens is thicker at the center and thinner at the edges. It can converge parallel light rays to a focus point. It can form both real images (when object is beyond focus) and virtual images (when object is between focus and lens).
The point where parallel rays of light converge after passing through a convex lens is called:
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Principal focus
The principal focus (F) is the point on the optic axis where light rays parallel to the axis converge after refraction through a convex lens. This is a fundamental definition in lens optics.
Which of the following statements about concave lenses are correct?
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They diverge light rays, They have negative focal length, They always form virtual images
Concave lenses are diverging lenses that spread out light rays. They have negative focal length and negative power. They always form virtual, erect, and diminished images regardless of object position.
An object 4 cm high is placed 15 cm from a convex lens of focal length 10 cm. What is the height of the image?
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8 cm
Given: h₀ = 4 cm, u = -15 cm, f = 10 cm. First find v: 1/10 = 1/v - 1/(-15), so 1/v = 1/10 - 1/15 = 1/30, v = 30 cm. Magnification m = v/u = 30/(-15) = -2. Image height hᵢ = m × h₀ = (-2) × 4 = -8 cm. The magnitude is 8 cm (negative indicates inverted).
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Sources & Official References
- Kerala Board of Public Examinations — keralapareekshabhavan.in
- National Education Policy 2020 — education.gov.in
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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