Chapter Exam

Unit 16: Optics — Online MCQ Test

Q: A ray is incident at an angle of incidence i on one surface of a small angle prism (with angle of prism A) and emerges normally from the opposite surface. If the refractive index of the material of the prism is μ, then the angle of incidence is nearly equal to:

Answer: B. μA — For a small angle prism, Snell's law at the first surface is sin(i) ≈ i = μr1. At the second surface, if it emerges normally, r2 = 0. Since A = r1 + r2, then r1 = A. Thus, i = μA.

Q: In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes:

Answer: B. four times — Fringe width β = λD/d. If D' = 2D and d' = d/2, then β' = λ(2D)/(d/2) = 4 * (λD/d) = 4β.

Q: The Brewster's angle i_b for an interface should be:

Answer: B. 45° 1), tan(i_b) > 1, so i_b > 45°. Since the angle must be less than 90°, 45° < i_b < 90°.

Q: A microscope has an objective of focal length 2 cm, eyepiece of focal length 4 cm and the tube length of 40 cm. If the distance of distinct vision of eye is 25 cm, the magnification in the microscope is

Answer: B. 125 — For a compound microscope, M = (L/fo) * (D/fe) = (40/2) * (25/4) = 20 * 6.25 = 125.

Q: An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of

Answer: A. large focal length and large diameter — Angular magnification of an astronomical telescope = f₀/fₑ, so a large focal length of the objective gives large magnification. Angular resolution is given by θ = 1.22λ/D; a larger diameter D gives smaller θ (better resolution). Hence, objective with large focal length and large diameter is required.

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Practice Unit 16: Optics with a free chapter-wise online MCQ test for NEET NEET (All) PHYSICS. This chapter covers: Reflection of light spherical mirrors morror formula. Refraction of light at plane and spherical surfaces thin lens formula and lens maker formula. Total internal reflection and it.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Unit 16: Optics — Important Questions & Answers (FAQ)

Frequently asked questions from NEET NEET (All) PHYSICS — Unit 16: Optics, with answers and explanations. These are sample questions; the exam has its own separate question set.

A ray is incident at an angle of incidence i on one surface of a small angle prism (with angle of prism A) and emerges normally from the opposite surface. If the refractive index of the material of the prism is μ, then the angle of incidence is nearly equal to:

A. 2A
B. μA ✓
C. A/2μ
D. 2μA

Answer: B. μA
For a small angle prism, Snell's law at the first surface is sin(i) ≈ i = μr1. At the second surface, if it emerges normally, r2 = 0. Since A = r1 + r2, then r1 = A. Thus, i = μA.

In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes:

A. half
B. four times ✓
C. one-fourth
D. double

Answer: B. four times
Fringe width β = λD/d. If D' = 2D and d' = d/2, then β' = λ(2D)/(d/2) = 4 * (λD/d) = 4β.

The Brewster's angle i_b for an interface should be:

A. 30° < i_b < 45°
B. 45° < i_b < 90° ✓
C. i_b = 90°
D. 0° < i_b < 30°

Answer: B. 45° < i_b < 90°
Brewster's angle is defined by tan(i_b) = n₂/n₁. For the transition from air to a denser medium (n > 1), tan(i_b) > 1, so i_b > 45°. Since the angle must be less than 90°, 45° < i_b < 90°.

A microscope has an objective of focal length 2 cm, eyepiece of focal length 4 cm and the tube length of 40 cm. If the distance of distinct vision of eye is 25 cm, the magnification in the microscope is

A. 100
B. 125 ✓
C. 150
D. 250

Answer: B. 125
For a compound microscope, M = (L/fo) * (D/fe) = (40/2) * (25/4) = 20 * 6.25 = 125.

An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of

A. large focal length and large diameter ✓
B. large focal length and small diameter
C. small focal length and large diameter
D. small focal length and small diameter

Answer: A. large focal length and large diameter
Angular magnification of an astronomical telescope = f₀/fₑ, so a large focal length of the objective gives large magnification. Angular resolution is given by θ = 1.22λ/D; a larger diameter D gives smaller θ (better resolution). Hence, objective with large focal length and large diameter is required.