Q11. Which of the following statements are correct?
A. A Equi Convex lens of f = 20 cm is cut as the

Q: What is the correct answer for CUET UG Physics Q11?

The correct answer is D. Let's analyze each statement: **B. A Equi Convex lens of f = 20 cm is cut as the focal length of each part is 20 cm.** This statement is correct if the lens is cut perpendicular to its principal axis (e.g., horizontally into two thinner lenses). In this case, the radius of curvature of the surfaces remains the same for each part, and thus the focal length of each part remains the same as the origi

Q: Q11. Which of the following statements are correct? A. A Equi Convex lens of f = 20 cm is cut as the focal length of each part is 10 cm. B. A Equi Convex lens of f = 20 cm is cut as the focal length…

The correct answer is D. Let's analyze each statement: **B. A Equi Convex lens of f = 20 cm is cut as the focal length of each part is 20 cm.** This statement is correct if the lens is cut perpendicular to its principal axis (e.g., horizontally into two thinner lenses). In this case, the radius of curvature of the surfaces remains the same for each part, and thus the focal length of each part remains the same as the origi

Q: What are the options for this CUET UG Physics question?

A. A, B only · B. A, B, c only · C. B, C Only · D. B, C, D Only

Question

Q11. Which of the following statements are correct?
A. A Equi Convex lens of f = 20 cm is cut as the focal length of each part is 10 cm.
B. A Equi Convex lens of f = 20 cm is cut as the focal length of each part is 20 cm.
C. If an Equi Convex lens of refractive index µ₁ is placed in a liquid of (µ2) such that (μ₁ > µ2). It will not change it's nature.
D. A Convex lens of f = 20 cm is cut as the focal length of each part is 40 cm.
Choose the correct answer from the options given below:
(a) A, B only
(b) A, B, c only
(c) B, C Only
(d) B, C, D Only

FirstInTest · Accepted Answer

Let's analyze each statement:
**B. A Equi Convex lens of f = 20 cm is cut as the focal length of each part is 20 cm.** This statement is correct if the lens is cut perpendicular to its principal axis (e.g., horizontally into two thinner lenses). In this case, the radius of curvature of the surfaces remains the same for each part, and thus the focal length of each part remains the same as the original lens, i.e., 20 cm. The intensity of the image would, however, decrease.
**C. If an Equi Convex lens of refractive index µ₁ is placed in a liquid of (µ2) such that (μ₁ > µ2). It will not change it's nature.** This statement is correct. The nature of a lens (converging or diverging) depends on its refractive index relative to the surrounding medium. If the refractive index of the lens (μ₁) is greater than that of the medium (μ₂), a convex lens will retain its converging nature. It would only change its nature if μ₁ < μ₂.
**D. A Convex lens of f = 20 cm is cut as the focal length of each part is 40 cm.** This statement is correct if the lens is cut along its principal axis (e.g., vertically into two plano-convex lenses). For an equiconvex lens, the lens maker's formula is 1/f = (μ-1)(1/R - (-1/R)) = 2(μ-1)/R. If cut along the principal axis, each part becomes a plano-convex lens with one curved surface of radius R and one plane surface (R=∞). For such a part, 1/f' = (μ-1)(1/R - 1/∞) = (μ-1)/R. Comparing, f' = 2f. So, if the original focal length f = 20 cm, then f' = 2 * 20 cm = 40 cm.
**A. A Equi Convex lens of f = 20 cm is cut as the focal length of each part is 10 cm.** This statement is incorrect as per the derivations above.
Therefore, statements B, C, and D are correct.

Answer

A, B only

Answer

A, B, c only

Answer

B, C Only

Answer

B, C, D Only

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