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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

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

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. 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).

3. 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.

4. 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.

5. 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.

6. 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).

7. 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.

8. 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.

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. 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.

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