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Question

Convex side of a plano-convex lens is fully immersed in a liquid, of same refractive index (equal to 8/5) as that of the lens. Which one among the following is correct regarding the image of a point source of light placed in air at 40 cm away from the lens? (Assume the focal length of the plano-convex lens as 20 cm)

This question was previously asked in
CDS 2 2026 Maths Question Paper (13-Sep-2026)
The correct answer is

No image will be formed because of the same refractive index of the lens and the liquid

As per the official Series A provisional answer key, no image is formed because the lens and liquid share the same refractive index.

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Important Questions from Refraction and Reflection

  1. A convex lens of focal length f will form a magnified real image of an object, if the object is placed.

  2. A ray of light travelling in the direction \(\frac{1}{2} (\hat i + \sqrt 3 \hat j)\) is incident on a plane mirror. After reflection it travels along the direction  \(\frac{1}{2} (\hat i - \sqrt 3 \hat j)\)  The angle of incidence is:

  3. Twinkling of stars is due to atmospheric

  4. An optical fibre has a core material of refractive index of 1.55 and cladding material of refractive index of 1.50. The numerical aperture of the fibre is

  5. The refracting angle of a prism is $A$. The refractive index of the material of the prism is $\frac{1+\cos A}{\sin A}$. The angle of minimum deviation is:
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