Science MCQ, Class 10th, Chapter-9, Light: Reflection and Refraction

NCERT based MCQ of Class 10th, Chapter-9, Light: Reflection and Refraction with brief explanation for competitive exams like TGT HTET, KVS PGT, TGT NVS, TGT EMRS, SSC and all other state competition exams.

Along with MCQ, Chapter Key-Points for quick learning NCERT related facts are also discussed below.

Right Answer for MCQ will be highlighted on Hover / Click on the option. 

Summary of the Chapter-9-Light: Reflection and Refraction with Key-Points:

• Light generally moves in straight paths.
• Mirrors and lenses create images, which can be real or virtual depending on where the object is placed.
• All reflective surfaces adhere to the laws of reflection, and refractive surfaces follow the principles of refraction.
• New Cartesian sign conventions are used for spherical mirrors and lenses.
• The mirror equation, 1/v + 1/u = 1/f, relates object distance (u), image distance (v), and focal length (f) in spherical mirrors.
• The focal length of a spherical mirror is half of its radius of curvature.
• Magnification by a spherical mirror is the ratio of the image’s height to the object’s height.
• A light ray moving from a denser to a rarer medium bends away from the normal, while a ray going from a rarer to a denser medium bends towards the normal.
• Light travels through a vacuum at a speed of 3 * 10⁸ m/s, but its speed changes depending on the medium.
• The refractive index of a medium is the ratio of the speed of light in a vacuum to its speed in that medium.
• In a rectangular glass slab, refraction happens at both the air-glass and glass-air boundaries, and the emergent ray remains parallel to the incident ray.
• The lens formula, 1/v - 1/u = 1/f, connects the object distance (u), image distance (v), and focal length (f) for spherical lenses.
• The power of a lens is the inverse of its focal length, and its SI unit is the diopter (D).
  

NCERT Based MCQ with Explanation:

1. Which of the following statements is correct about light?

(A) Light can only travel through a vacuum.

(B) Light travels in straight lines.

(C) Light cannot pass through transparent objects.

(D) Light can be seen in a dark room.

Explanation: Light typically travels in straight lines, which is why we see sharp shadows when light is blocked by an object. This concept is known as rectilinear propagation of light. The observation of this straight-line travel can be seen through phenomena such as the casting of shadows and the way light reflects off surfaces.

2. The angle of incidence is:

(A) Greater than the angle of reflection.

(B) Always equal to the angle of refraction.

(C) Equal to the angle of reflection.

(D) Smaller than the angle of reflection.

Explanation: According to the law of reflection, the angle of incidence is always equal to the angle of reflection, regardless of the type of reflecting surface. This applies to both plane mirrors and spherical mirrors.

3. Which of the following is true for the image formed by a plane mirror?

(A) The image is real and inverted.

(B) The image is virtual and inverted.

(C) The image is virtual and erect.

(D) The image is real and erect.

Explanation: A plane mirror forms a virtual image, which means it cannot be projected on a screen. The image is also erect and laterally inverted (the left and right sides are switched), and it appears behind the mirror at the same distance as the object in front of it.

4. In a concave mirror, parallel rays of light after reflection:

(A) Diverge away from each other.

(B) Converge at the pole of the mirror.

(C) Converge at the focus of the mirror.

(D) Travel along the principal axis without deviation.

Explanation: When parallel rays of light fall on a concave mirror, they reflect and converge at a single point called the focus, which lies on the principal axis in front of the mirror.

5. What is the focal length of a spherical mirror with a radius of curvature of 20 cm?

(A) 40 cm

(B) 20 cm

(C) 10 cm

(D) 5 cm

Explanation: The focal length (f) of a spherical mirror is half of the radius of curvature (R). The formula is f = R/2. Given the radius of curvature R = 20 cm, the focal length will be f = 20/2 = 10 cm.

6. A convex mirror is often used:

(A) In solar furnaces.

(B) As a shaving mirror.

(C) As a rear-view mirror in vehicles.

(D) In searchlights.

Explanation: Convex mirrors are used as rear-view mirrors in vehicles because they provide a wide field of view and form erect, diminished images, allowing drivers to see a larger area of traffic behind them.

7. If an object is placed at the center of curvature of a concave mirror, the image formed will be:

(A) Virtual, inverted, and enlarged.

(B) Real, inverted, and of the same size as the object.

(C) Real, inverted, and diminished.

(D) Virtual, erect, and of the same size.

Explanation: When an object is placed at the center of curvature of a concave mirror, the image is formed at the same point and is real, inverted, and of the same size as the object.

8. In a concave mirror, when the object is placed between the pole and the focus, the image formed is:

(A) Real, inverted, and diminished.

(B) Virtual, erect, and enlarged.

(C) Virtual, inverted, and diminished.

(D) Real, erect, and enlarged.

Explanation: When the object is placed between the pole and the focus of a concave mirror, the image formed is virtual, erect, and larger than the object. It appears behind the mirror.

9. In refraction, when light passes from a rarer to a denser medium, it:

(A) Bends towards the normal.

(B) Bends away from the normal.

(C) Travels in a straight line without bending.

(D) Gets reflected back into the rarer medium.

Explanation: When light enters a denser medium from a rarer one (such as from air into water), it slows down and bends towards the normal. This bending is due to the change in the speed of light.

10. The refractive index of a medium is the ratio of:

(A) Speed of light in the medium to the speed of light in vacuum.

(B) Speed of light in vacuum to the speed of light in the medium.

(C) The wavelength of light in the medium to the wavelength in vacuum.

(D) Frequency of light in vacuum to the frequency in the medium.

Explanation: The refractive index is a measure of how much light bends when it enters a medium. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium.

11. What happens to light as it passes through a rectangular glass slab?

(A) It bends away from the normal at both the surfaces.

(B) It bends towards the normal at both the surfaces.

(C) It bends towards the normal at one surface and away from the normal at the other surface.

(D) It doesn't bend at all.

Explanation: When light passes through a rectangular glass slab, it bends towards the normal as it enters the denser medium (glass) and bends away from the normal when it exits into the rarer medium (air). The emergent ray is parallel to the incident ray.

12. A concave mirror forms a real, inverted, and diminished image of an object. The object is placed:

(A) Between the pole and focus.

(B) Between the focus and the center of curvature.

(C) Beyond the center of curvature.

(D) At the focus.

Explanation: When an object is placed beyond the center of curvature of a concave mirror, the image formed is real, inverted, and smaller than the object.

13. A convex mirror always forms:

(A) A real, diminished, and inverted image.

(B) A virtual, diminished, and erect image.

(C) A real, enlarged, and inverted image.

(D) A virtual, enlarged, and erect image.

Explanation: A convex mirror always forms a virtual image that is diminished and erect, irrespective of the position of the object. This is why convex mirrors are used as rear-view mirrors in vehicles.

14. Which of the following is NOT a use of concave mirrors?

(A) In torches.

(B) In solar furnaces.

(C) As rear-view mirrors.

(D) As shaving mirrors.

Explanation: Concave mirrors are used in torches, solar furnaces, and shaving mirrors due to their ability to focus light and form enlarged, upright images. Convex mirrors are used as rear-view mirrors in vehicles because they form diminished and erect images.

15. What is the focal length of a convex mirror with a radius of curvature of 30 cm?

(A) 30 cm

(B) 20 cm

(C) 15 cm

(D) 10 cm

Explanation: The focal length f of a spherical mirror is half the radius of curvature R. For a convex mirror, f = R/2 = 30/2 = 15 cm.

16. If the focal length of a concave mirror is 20 cm, its radius of curvature will be:

(A) 10 cm

(B) 20 cm

(C) 40 cm

(D) 80 cm

Explanation: The radius of curvature R of a mirror is twice the focal length f. Therefore, if f = 20 cm, R = 2f = 40 cm.

17. A ray of light incident along the normal to the surface of a glass slab:

(A) Is reflected back along the same path.

(B) Is refracted away from the normal.

(C) Passes through the glass slab without deviation.

(D) Is absorbed by the glass slab.

Explanation: When a ray of light is incident along the normal (perpendicular) to the surface of a glass slab, it passes through without bending because the angle of incidence is 0°, and no refraction occurs.

18. The radius of curvature of a concave mirror is 40 cm. What is its focal length?

(A) 10 cm

(B) 20 cm

(C) 40 cm

(D) 80 cm

Explanation: For concave mirrors, the focal length f is half of the radius of curvature R. If the radius of curvature R = 40 cm, then the focal length f = 40/2 = 20 cm.

19. When light passes from air into water, the speed of light:

(A) Increases.

(B) Decreases.

(C) Remains the same.

(D) Is unaffected by the medium.

Explanation: Light slows down when it enters a denser medium, such as water, because the molecules in the denser medium obstruct the light's path more than the air molecules do. This change in speed is what causes refraction.

20. A concave mirror is used to form a real, inverted image of the same size as the object. The object must be placed:

(A) Between the focus and the pole of the mirror.

(B) Between the center of curvature and the focus.

(C) At the center of curvature.

(D) Beyond the center of curvature.

Explanation: When the object is placed at the center of curvature of a concave mirror, the image formed is real, inverted, and the same size as the object. The image is also formed at the center of curvature.

21. A convex mirror is used in vehicles as a rear-view mirror because:

(A) It produces a magnified image of vehicles behind.

(B) It gives a wider field of view.

(C) It produces a virtual and inverted image.

(D) It focuses light to a point behind the mirror.

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22. In a concave mirror, if the object is placed at the principal focus, the image will be formed:

(A) At infinity.

(B) At the pole of the mirror.

(C) Between the focus and the center of curvature.

(D) At the center of curvature.

23. When light travels from water into air, it:

(A) Bends towards the normal.

(B) Bends away from the normal.

(C) Does not bend at all.

(D) Is reflected completely.

24. The refractive index of a medium is:

(A) Greater than 1 for all transparent materials.

(B) Less than 1 for all transparent materials.

(C) Equal to 1 for all transparent materials.

(D) Infinite for all transparent materials.

25. A ray of light passes from air into a glass block at an angle of incidence of 30°. If the angle of refraction is 20°, what is the refractive index of glass relative to air?

(A) 0.66

(B) 1.33

(C) 1.5

(D) 1.76

26. The image formed by a convex mirror is always:

(A) Real and diminished.

(B) Virtual and diminished.

(C) Real and enlarged.

(D) Virtual and enlarged.

27. What is the power of a concave lens with a focal length of 20 cm?

(A) -2.0 D

(B) 2.0 D

(C) -5.0 D

(D) 5.0 D

28. The magnification produced by a convex mirror is:

(A) Always greater than 1.

(B) Always less than 1.

(C) Equal to 1.

(D) Always negative.

29. In which of the following situations would you expect the image to be virtual, erect, and larger than the object?

(A) Object placed between the focus and the pole of a concave mirror.

(B) Object placed at the center of curvature of a concave mirror.

(C) Object placed beyond the center of curvature of a concave mirror.

(D) Object placed at the focus of a concave mirror.

30. A ray of light passes through the optical center of a convex lens. It will:

(A) Bend towards the normal.

(B) Bend away from the normal.

(C) Pass through without any deviation.

(D) Be reflected back along the same path.

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