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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. Which optical instrument uses total internal reflection to transmit light signals through flexible glass fibers?

  1. Astronomical telescope
  2. Optical fiber
  3. Compound microscope
  4. Simple magnifying glass
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Answer: B

Optical fibers rely on continuous total internal reflection inside a high-purity glass core to transmit light over long distances.

2. 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.

3. Where should an object be placed in front of a convex lens to act as a simple magnifying glass?

  1. At the focal point (u = f)
  2. Between the optical centre and the focal point (u < f)
  3. Between f and 2f
  4. Beyond 2f
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Answer: B

When u < f, a convex lens forms an upright, virtual, and magnified image on the same side as the object, functioning as a magnifying glass.

4. 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).

5. 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.

6. Which lens focal length combination is best suited for constructing a high-magnification compound microscope?

  1. Objective f_o = 1 cm, Eyepiece f_e = 5 cm
  2. Objective f_o = 100 cm, Eyepiece f_e = 5 cm
  3. Objective f_o = 50 cm, Eyepiece f_e = 50 cm
  4. Objective f_o = 5 cm, Eyepiece f_e = 0.5 cm
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Answer: A

A compound microscope requires a very short objective focal length (f_o) and a slightly longer eyepiece focal length (f_e), with f_o < f_e.

7. 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.

8. A concave lens with a focal length of 20 cm produces an image of an object placed 20 cm in front of it. What is the image distance v?

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

For a concave lens, f is negative (f = -20 cm). 1f = 1u + 1v => -120 = 120 + 1v => 1v = -120 - 120 = -220 = -110 => v = -10 cm (virtual image 10 cm in front of lens).

9. Which of the following conditions must be met for total internal reflection to occur?

  1. Light must travel from an optically less dense medium to a denser medium
  2. The angle of incidence must be smaller than the critical angle
  3. Light must travel from an optically denser medium to a less dense medium, and angle of incidence > critical angle
  4. The angle of refraction must equal 0°
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Answer: C

Total internal reflection requires light to travel from a denser to a less dense medium with an angle of incidence exceeding the critical angle.

10. If an object is placed at 2f in front of a convex lens, what are the characteristics of the image formed?

  1. Virtual, upright, magnified
  2. Real, inverted, same size as object
  3. Real, inverted, diminished
  4. Virtual, inverted, same size
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Answer: B

When u = 2f, the convex lens forms a real, inverted image at v = 2f with linear magnification m = 1 (same size as object).

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