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Quiz Chapter 6: Light and Optics

10 questions · Form 4 Physics Bab 5: Light and Optics

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. Why are convex mirrors preferred as road blind-spot safety mirrors at sharp corners?

  1. They form magnified images of oncoming cars
  2. They provide an upright image with a wider field of view
  3. They focus sunlight to improve visibility at night
  4. They invert images so drivers pay closer attention
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Answer: B

Convex mirrors produce diminished, upright images, enabling a wider field of view for drivers around dangerous blind curves.

2. What is the linear magnification of an image formed 30 cm from a lens when the object distance is 15 cm?

  1. 0.5
  2. 2.0
  3. 3.0
  4. 1.5
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Answer: B

Linear magnification m = vu = 30 cm / 15 cm = 2.0.

3. A ray of light strikes a glass prism with a critical angle of 42°. Which ray path occurs if the angle of incidence inside the glass is 45°?

  1. Light undergoes refraction into the air at 90°
  2. Light undergoes total internal reflection back into the glass
  3. Light passes straight through without bending
  4. Light is completely absorbed
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Answer: B

Since light is in the denser medium and the angle of incidence (45°) exceeds the critical angle (42°), total internal reflection occurs.

4. Light travels from air into a glass block at an angle of incidence of 30°. If the refractive index of glass is 1.5, what is the angle of refraction?

  1. 19.5°
  2. 48.6°
  3. 15.0°
  4. 22.1°
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Answer: A

Using Snell's Law: n = sin(i) / sin(r) => 1.5 = sin(30°) / sin(r) => sin(r) = 0.51.5 = 0.3333 => r = sin-1(0.3333) ≈ 19.5°.

5. Which device uses a concave mirror to produce a parallel beam of reflected light?

  1. Car headlight reflector
  2. Security rear-view mirror in convenience stores
  3. Passenger-side car side mirror
  4. Periscope
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Answer: A

Car headlights place a light bulb at the focal point of a concave parabolic mirror to project a strong, parallel beam of light.

6. An astronomical telescope has an objective lens focal length of 80 cm and an eyepiece focal length of 5 cm. Calculate its magnifying power.

  1. 16
  2. 400
  3. 85
  4. 0.0625
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Answer: A

Magnifying power M = f_of_e = 80 cm / 5 cm = 16.

7. A swimming pool has a real depth of 2.4 m. If the refractive index of water is 1.33, what is its apparent depth?

  1. 3.19 m
  2. 1.80 m
  3. 2.00 m
  4. 1.20 m
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Answer: B

Using n = Real depth / Apparent depth => Apparent depth = Real depth / n = 2.41.33 ≈ 1.80 m.

8. A concave mirror has a radius of curvature of 20 cm. What is its focal length?

  1. 10 cm
  2. 40 cm
  3. 20 cm
  4. 5 cm
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Answer: A

The relationship between radius of curvature (r) and focal length (f) is r = 2f. Therefore, f = r2 = 202 = 10 cm.

9. What is the speed of light in a glass block whose refractive index is 1.50?

  1. 2.0 × 108 m s-1
  2. 3.0 × 108 m s-1
  3. 4.5 × 108 m s-1
  4. 1.5 × 108 m s-1
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Answer: A

Using n = cv => v = cn = 3.0 × 1081.50 = 2.0 × 108 m s-1.

10. What happens to a ray of light passing through the optical centre (O) of a thin lens?

  1. It bends towards the focal point
  2. It reflects straight back along its path
  3. It continues straight without undergoing deviation
  4. It bends parallel to the principal axis
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Answer: C

Light rays passing directly through the optical centre (O) pass unbent (undeviated).

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