Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEETPhysicsRay Optics

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): When a convex lens is cut into two identical halves along its principal axis, the focal length of each half becomes half of the original value, and the intensity of the image remains unchanged. Reason (R): When cut along the principal axis, the radii of curvature of the lens remain unchanged, while

Options

  1. ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
  2. BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
  3. CAssertion (A) is true but Reason (R) is false.
  4. DAssertion (A) is false but Reason (R) is true.

Correct answer

D. Assertion (A) is false but Reason (R) is true.

Step-by-step solution

The focal length of a lens is given by the Lens Maker's formula: 1 f = ( - 1) ( 1 R₁ - 1 R₂ ) . When a lens is cut along its principal axis, the radii of curvature ( R₁ and R₂ ) of the two halves remain the same as that of the original lens. Therefore, the focal length of each half remains unchanged. The Assertion states that the focal length becomes half, which is incorrect. Furthermore, the intensity of the image formed by a lens is directly proportional to its aperture area. Since cutting the lens along the prin

Practice Ray Optics on Quantrex Academy →

More from Ray Optics

A container is filled with water ( = 4/3 ) up to a height of 24 cm. A concave mirror is placed 10 cm above the water level, and the image (I) of an object placed at the bottom is f 2026The refracting angle of a prism is 'A' and its refractive index is ( A 2 ) . The minimum deviation produced by the prism is 2026A circular beam of light having diameter 'd' falls on a plane liquid surface from air. The angle of incidence is 45^ and refractive index of liquid is 'n'. The diameter of the refr 2026What is the total optical path length of two media in contact with thicknesses of d and d 4 and refractive indices of n₁ and n₂ , respectively? 2026A beam of white light is allowed to pass through convex lens parallel to principal axis, the different colours of light converge at different points on the principle axis after ref 2026The angle of minimum deviation produced by a thin prism in air is ₁ . What will be the minimum deviation ( ₂) if the prism is immersed in another liquid medium? _a n_g = 3/2, _a n_ 2026A ray of light passes through four transparent media with refractive indices ₁ , ₂ , ₃ and ₄ as shown in the figure. The surfaces of all media are parallel. If the emergent ray CD 2026The thin prism having refracting angle 10^ is made of glass of refractive index 1.42 . This prism is combined with another thin prism of glass of refractive index 1.7 . This combin 2026 Full Ray Optics list All NEET PYQs