Light Reflection and Refraction (Class 10 Science)

Light travels in straight lines and can be reflected and refracted when it encounters different surfaces and media. Understanding reflection and refraction

Light Reflection and Refraction (Class 10 Science)

Light travels in straight lines and can be reflected and refracted when it encounters different surfaces and media. Understanding reflection and refraction

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TL;DR: Light travels in straight lines and can be reflected and refracted when it encounters different surfaces and media. Understanding reflection and refra…

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Light travels in straight lines and can be reflected and refracted when it encounters different surfaces and media. Understanding reflection and refraction

Light Reflection and Refraction MCQs with Answers & Explanations

Q1. What is the angle of incidence if the angle of reflection is 35 degrees?

  1. 35 degrees ✓ (correct)
  2. 45 degrees
  3. 55 degrees
  4. 70 degrees

Explanation: According to the law of reflection, the angle of incidence equals the angle of reflection, so if reflection is 35 degrees, incidence is also 35 degrees.

Q2. Which of the following is true about a concave mirror when the object is at the center of curvature?

  1. Image is virtual and upright
  2. Image is real and same size ✓ (correct)
  3. Image is virtual and magnified
  4. Image is real and diminished

Explanation: When an object is placed at the center of curvature of a concave mirror, the image formed is real, inverted, and equal in size to the object.

Q3. The focal length of a plane mirror is:

  1. Equal to its radius of curvature
  2. Half its radius
  3. Infinite ✓ (correct)
  4. Zero

Explanation: A plane mirror has an infinite focal length because its radius of curvature is infinite, so it does not converge or diverge light rays.

Q4. When light travels from a denser to a rarer medium, it bends:

  1. Towards the normal
  2. Parallel to the normal
  3. At right angles to the normal
  4. Away from the normal ✓ (correct)

Explanation: When light travels from a denser to a rarer medium, it bends away from the normal because the speed of light increases in the rarer medium.

Q5. What is the power of a lens with focal length 25 cm?

  1. +4.0 diopters ✓ (correct)
  2. +2.5 diopters
  3. +0.4 diopters
  4. -4.0 diopters

Explanation: Power of lens = 1/focal length in meters. With f = 0.25 m, power = 1/0.25 = 4.0 diopters for a converging lens.

Q6. A convex lens forms a real, inverted and diminished image when the object is:

  1. At the focal point
  2. Beyond the center of curvature ✓ (correct)
  3. Between focal point and center
  4. At infinity

Explanation: For a convex lens the image is real, inverted and diminished when the object lies beyond 2F (the centre of curvature). With the object at infinity the image is a point at the focus, not simply "diminished".

Q7. The refractive index of a medium is always:

  1. Less than 1
  2. Equal to 1
  3. Greater than or equal to 1 ✓ (correct)
  4. Negative

Explanation: The refractive index is the ratio of speed of light in vacuum to speed in the medium, so it is always greater than or equal to 1.

Q8. Which mirror is used in a car headlight?

  1. Cylindrical mirror
  2. Convex mirror
  3. Plane mirror
  4. Concave mirror ✓ (correct)

Explanation: A concave mirror is used in car headlights because it converges light rays from the bulb to produce a parallel beam of light ahead.

Q9. If a convex lens of focal length 10 cm is used as a magnifying glass, where should the object be placed?

  1. Between the focal point and the center ✓ (correct)
  2. At the center of curvature
  3. Beyond the center of curvature
  4. At the focal point

Explanation: For a magnifying glass, the object should be placed between the focal point and the lens to get a virtual, upright, and magnified image.

Q10. The critical angle for total internal reflection depends on:

  1. Angle of incidence only
  2. The refractive indices of the two media ✓ (correct)
  3. The color of light only
  4. The wavelength of light only

Explanation: The critical angle depends on the refractive indices of the two media involved in the refraction process, not on the color or wavelength.

Frequently Asked Questions

What is the difference between reflection and refraction?

Reflection is the bouncing back of light from a surface, while refraction is the bending of light when it passes from one medium to another.

Why do we see a rainbow after rain?

Rainbows form due to dispersion of sunlight through water droplets, where different colors of light refract at different angles.

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