Chapter Exam

Chapter 4: Refraction of Light at Curved Surfaces — Online MCQ Test

Q: An object is placed at the center of curvature of a convex lens. Where will the image form?

Answer: B. At the center of curvature on the opposite side — When an object is at 2F (center of curvature), the image forms at 2F on the opposite side with magnification m = -1, producing a real, inverted, and equal-sized image.

Q: What happens to the focal length of a lens when it is immersed in water?

Answer: B. Focal length increases — When a lens is immersed in a medium like water, the relative refractive index (n_lens/n_medium) decreases, causing the focal length to increase and optical power to decrease.

Q: A student uses a convex lens to form a real, inverted image that is twice the size of the object. If the object distance is 30 cm, what is the focal length of the lens?

Answer: C. 20 cm — Given m = -2 (inverted magnification), m = -v/u → -2 = -v/30 → v = 60 cm. Using 1/f = 1/v + 1/u = 1/60 + 1/30 = 3/60 = 1/20 → f = 20 cm.

PHYSICAL SCIENCES · CLASS 10th · Telangana State Board

Practice Chapter 4: Refraction of Light at Curved Surfaces with a free chapter-wise online MCQ test for Telangana State Board CLASS 10th PHYSICAL SCIENCES. This chapter covers: Extending optics to curved interfaces this chapter focuses on how light bends when passing through spherical lenses (convex and concave). Students explore concepts like principal f.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 4: Refraction of Light at Curved Surfaces — Important Questions & Answers (FAQ)

Frequently asked questions from Telangana State Board CLASS 10th PHYSICAL SCIENCES — Chapter 4: Refraction of Light at Curved Surfaces, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the optical center of a lens?

A. The geometric center of the lens where light passes undeviated ✓
B. The point where all light rays converge
C. The point on the principal axis at distance f from the lens
D. The point where the lens is thickest

Answer: A. The geometric center of the lens where light passes undeviated
The optical center is the geometric center of the lens through which light passes without bending, regardless of the angle of incidence.

Define the principal focus of a convex lens.

A. The point where parallel rays converge after refraction through the lens ✓
B. The center of curvature of the lens surface
C. The point equidistant from both surfaces of the lens
D. The virtual point from which rays appear to diverge

Answer: A. The point where parallel rays converge after refraction through the lens
The principal focus (F) of a convex lens is the point on the principal axis where all parallel rays converge after passing through the lens.

An object is placed at the center of curvature of a convex lens. Where will the image form?

A. At the focal point
B. At the center of curvature on the opposite side ✓
C. At infinity
D. Between the focal point and center of curvature

Answer: B. At the center of curvature on the opposite side
When an object is at 2F (center of curvature), the image forms at 2F on the opposite side with magnification m = -1, producing a real, inverted, and equal-sized image.

What happens to the focal length of a lens when it is immersed in water?

A. Focal length remains the same
B. Focal length increases ✓
C. Focal length decreases
D. Focal length becomes zero

Answer: B. Focal length increases
When a lens is immersed in a medium like water, the relative refractive index (n_lens/n_medium) decreases, causing the focal length to increase and optical power to decrease.

A student uses a convex lens to form a real, inverted image that is twice the size of the object. If the object distance is 30 cm, what is the focal length of the lens?

A. 10 cm
B. 15 cm
C. 20 cm ✓
D. 25 cm

Answer: C. 20 cm
Given m = -2 (inverted magnification), m = -v/u → -2 = -v/30 → v = 60 cm. Using 1/f = 1/v + 1/u = 1/60 + 1/30 = 3/60 = 1/20 → f = 20 cm.

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