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UP Board Class 10 Refraction of Light and Lenses — practice questions — page 4

Explore 144 free Refraction of Light and Lenses questions in UP Board Class 10 Science. Open each question or exercise to read its content, reference answers and available explanation.

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Refraction of Light and Lenses questions and exercises with answers

Showing questions 91–120 of 144.

The absolute refractive index of a medium is the ratio of:Read the answer and worked solution →The refractive index of water is 1.33. The speed of light in water (in m/s) is approximately:Read the answer and worked solution →A ray of light travels from air into a glass slab. Which of the following changes is correct?Read the answer and worked solution →In a glass slab, a ray of light is refracted twice. The emergent ray is:Read the answer and worked solution →A convex lens forms a real image when the object is placed:Read the answer and worked solution →Power of a lens is measured in:Read the answer and worked solution →A lens has focal length 50 cm. Its power is:Read the answer and worked solution →A concave lens has a focal length of -25 cm. Its power is:Read the answer and worked solution →Two thin lenses of power +3 D and -1 D are kept in contact. The net power is:Read the answer and worked solution →A concave mirror with focal length 20 cm forms an image at 30 cm in front of it. The object is at:Read the answer and worked solution →For a concave mirror, magnification is +3 (virtual, erect, enlarged). If image is at +60 cm, object is at:Read the answer and worked solution →Which property of the image makes a convex mirror preferred for rear-view?Read the answer and worked solution →Lateral inversion in a plane mirror means:Read the answer and worked solution →Refractive index of medium A with respect to medium B is given by:Read the answer and worked solution →Light travelling from air strikes a water surface at 0° to the normal. The angle of refraction is:Read the answer and worked solution →A pencil partially dipped in water appears bent at the surface. This is due to:Read the answer and worked solution →A convex lens of focal length 20 cm produces a real image at distance 60 cm. The object is at:Read the answer and worked solution →A real image formed by a convex lens is:Read the answer and worked solution →The principal focus of a concave lens is:Read the answer and worked solution →A lens forms an image of an object placed at twice its focal length. The image is:Read the answer and worked solution →The focal length of a plane mirror is:Read the answer and worked solution →A diverging lens is also called:Read the answer and worked solution →The light-sensitive layer at the back of the eyeball is the:Read the answer and worked solution →Most of the refraction of light entering the eye occurs at the:Read the answer and worked solution →The size of the pupil is controlled by the:Read the answer and worked solution →The ability of the eye to focus on objects at different distances by adjusting the focal length of the lens is called:Read the answer and worked solution →The least distance of distinct vision for a young adult is approximately:Read the answer and worked solution →The far point of a normal eye is:Read the answer and worked solution →Myopia is corrected using a:Read the answer and worked solution →Hypermetropia is corrected using a:Read the answer and worked solution →

Worked practice questions

The absolute refractive index of a medium is the ratio of:

  1. Angle of incidence to angle of refraction
  2. Speed in the medium to speed in vacuum
  3. Speed of light in vacuum to speed in the medium
  4. Frequency of light to wavelength
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Correct answer: C. Speed of light in vacuum to speed in the medium

1. Absolute refractive index n = c / v. 2. c is the speed of light in vacuum. 3. v is the speed of light in the medium. _Source: syllabus Science, Ch 9 "Light Reflection and Refraction", §9.3.1_

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The refractive index of water is 1.33. The speed of light in water (in m/s) is approximately:

  1. 1.33 × 10⁸
  2. 3.0 × 10⁸
  3. 4.5 × 10⁸
  4. 2.26 × 10⁸
Show answer and solution

Correct answer: D. 2.26 × 10⁸

1. v = c/n = (3 × 10⁸)/1.33. 2. Calculation: 3 × 10⁸ ÷ 1.33 ≈ 2.26 × 10⁸ m/s. 3. Hence light slows to ~226,000 km/s in water. _Source: syllabus Science, Ch 9 "Light Reflection and Refraction", §9.3.1_

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A ray of light travels from air into a glass slab. Which of the following changes is correct?

  1. Speed and wavelength both decrease
  2. Speed decreases, frequency decreases
  3. Wavelength increases, speed increases
  4. Frequency increases, speed decreases
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Correct answer: A. Speed and wavelength both decrease

1. When light enters a denser medium, its speed decreases. 2. Frequency stays the same; wavelength shortens (v = fλ). 3. Hence both speed and wavelength decrease together. _Source: syllabus Science, Ch 9 "Light Reflection and Refraction", §9.3.1_

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