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Quiz Chapter 6: Light and Optics

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

Question 1 of 10Score: 0

In an astronomical telescope at normal adjustment, what is the distance between the objective lens (f_o) and the eyepiece lens (f_e)?

Full Question List & Answer Key

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

1. In an astronomical telescope at normal adjustment, what is the distance between the objective lens (f_o) and the eyepiece lens (f_e)?

  1. f_o - f_e
  2. f_o + f_e
  3. f_o × f_e
  4. f_of_e
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Answer: B

At normal adjustment, the principal focal points of both lenses coincide, making the separation distance equal to f_o + f_e.

2. 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.

3. What type of image is formed by a convex mirror?

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

Convex mirrors always produce virtual, upright, and diminished images regardless of object position, providing a wide field of view.

4. An object is placed at a distance u = 15 cm from a convex lens of focal length f = 10 cm. Find the image distance v.

  1. 6 cm
  2. 30 cm
  3. 15 cm
  4. -30 cm
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Answer: B

Using 1f = 1u + 1v => 110 = 115 + 1v => 1v = 110 - 115 = 130 => v = 30 cm.

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 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.

7. What is the critical angle of a diamond with a refractive index of 2.42?

  1. 24.4°
  2. 41.8°
  3. 48.8°
  4. 30.0°
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Answer: A

Using n = 1 / sin(c) => sin(c) = 12.42 ≈ 0.4132 => c = sin-1(0.4132) ≈ 24.4°.

8. 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.

9. 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.

10. 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.

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