Class 10 Science NCERT MCQs-Chapter 9-Light

1) What is the angle of incidence?
a) The angle formed by the reflected ray and the normal
b) The angle formed by the incident ray and the surface
c) The angle formed by the incident ray and the normal
d) The angle formed between the reflected and incident rays
Answer: c) The angle formed by the incident ray and the normal
Explanation: The angle of incidence is measured between the incident ray and the normal at the point of incidence.

2) Which law of reflection is always true?
a) The angle of incidence is twice the angle of reflection.
b) The reflected ray lies in a different plane than the incident ray.
c) The angle of incidence is equal to the angle of reflection.
d) Light cannot reflect off smooth surfaces.
Answer: c) The angle of incidence is equal to the angle of reflection.
Explanation: According to the laws of reflection, the angle of incidence equals the angle of reflection.

3) What happens when light passes from a rarer medium to a denser medium?
a) It bends away from the normal.
b) It bends towards the normal.
c) It does not change direction.
d) It reflects entirely.
Answer: b) It bends towards the normal.
Explanation: When light enters a denser medium, its speed decreases, and it bends towards the normal.

4) What is the phenomenon of bouncing back of light into the same medium called?
a) Refraction
b) Dispersion
c) Reflection
d) Diffraction
Answer: c) Reflection
Explanation: Reflection occurs when light strikes a surface and bounces back into the same medium.

5) Which of the following is NOT a characteristic of a plane mirror?
a) The image is virtual.
b) The image is erect.
c) The image is laterally inverted.
d) The image is smaller than the object.
Answer: d) The image is smaller than the object.
Explanation: A plane mirror always forms an image that is the same size as the object.

6) The focal length of a spherical mirror is:
a) Equal to the radius of curvature
b) Twice the radius of curvature
c) Half the radius of curvature
d) Independent of the radius of curvature
Answer: c) Half the radius of curvature
Explanation: For a spherical mirror, the focal length (f) is related to the radius of curvature (R) by f=R/2f = R/2f=R/2.

7) What type of image is formed by a concave mirror when the object is placed between the focus and the pole?
a) Real, inverted, and enlarged
b) Virtual, erect, and enlarged
c) Real, erect, and diminished
d) Virtual, inverted, and diminished
Answer: b) Virtual, erect, and enlarged
Explanation: When an object is placed between the focus and the pole of a concave mirror, it forms a virtual, erect, and enlarged image.

8) The refractive index of a medium is defined as the ratio of:
a) The speed of light in vacuum to the speed of light in the medium
b) The wavelength of light in vacuum to that in the medium
c) The angle of incidence to the angle of refraction
d) The angle of refraction to the angle of incidence
Answer: a) The speed of light in vacuum to the speed of light in the medium
Explanation: The refractive index nnn is given by n=c/v, where c is the speed of light in vacuum, and vvv is the speed of light in the medium.

9) The image formed by a convex mirror is always:
a) Real, inverted, and enlarged
b) Real, erect, and diminished
c) Virtual, erect, and diminished
d) Virtual, inverted, and enlarged
Answer: c) Virtual, erect, and diminished
Explanation: A convex mirror always forms a virtual, erect, and diminished image irrespective of the object's position.

10) What happens when the angle of incidence exceeds the critical angle in a denser medium?
a) Light is absorbed.
b) Light undergoes refraction.
c) Total internal reflection occurs.
d) Light stops propagating.
Answer: c) Total internal reflection occurs.
Explanation: When the angle of incidence is greater than the critical angle, light reflects entirely back into the denser medium.

11) The power of a lens is measured in:
a) Watts
b) Dioptres
c) Lumens
d) Degrees
Answer: b) Dioptres
Explanation: The power of a lens is the reciprocal of its focal length (in meters) and is measured in dioptres.

12) Which lens always forms a virtual, erect, and diminished image?
a) Convex lens
b) Concave lens
c) Both convex and concave lenses
d) Plane lens
Answer: b) Concave lens
Explanation: A concave lens always forms a virtual, erect, and diminished image irrespective of the object's position.

13) What is the principal axis of a spherical mirror?
a) The line joining the pole and the focus
b) The line joining the center of curvature and the pole
c) A line perpendicular to the mirror’s surface
d) The diameter of the mirror
Answer: b) The line joining the center of curvature and the pole
Explanation: The principal axis is the line passing through the pole and the center of curvature of a spherical mirror.

14) The magnification produced by a convex mirror is:
a) Always greater than 1
b) Always less than 1
c) Equal to 1
d) Either greater or less than 1
Answer: b) Always less than 1
Explanation: A convex mirror always produces a diminished image, so the magnification is less than 1.

15) A ray of light passing through the center of curvature of a concave mirror:
a) Passes through the focus
b) Reflects back along the same path
c) Bends away from the principal axis
d) Forms an inverted image
Answer: b) Reflects back along the same path
Explanation: A ray passing through the center of curvature strikes the mirror perpendicularly and reflects back along the same path.

16) What is the critical angle?
a) The angle of incidence at which light is totally absorbed
b) The angle of refraction in a vacuum
c) The angle of incidence at which light is refracted along the surface
d) The angle of incidence at which reflection stops
Answer: c) The angle of incidence at which light is refracted along the surface
Explanation: The critical angle is the angle of incidence in a denser medium for which the angle of refraction is 90∘.

17) Which mirror is used as a rear-view mirror in vehicles?
a) Plane mirror
b) Concave mirror
c) Convex mirror
d) Parabolic mirror
Answer: c) Convex mirror
Explanation: Convex mirrors provide a wider field of view and are used as rear-view mirrors in vehicles.

18) When an object is at infinity, a concave mirror forms an image that is:
a) Real, inverted, and enlarged
b) Virtual, erect, and diminished
c) Real, inverted, and highly diminished
d) Virtual, inverted, and enlarged
Answer: c) Real, inverted, and highly diminished
Explanation: A concave mirror forms a highly diminished image at the focus when the object is at infinity.

19) Which lens is used to correct myopia (short-sightedness)?
a) Convex lens
b) Concave lens
c) Cylindrical lens
d) Bifocal lens
Answer: b) Concave lens
Explanation: A concave lens diverges light rays, allowing the image to form on the retina for a myopic eye.

20) What is the focal length of a plane mirror?
a) Zero
b) Infinite
c) Equal to the radius of curvature
d) Cannot be determined
Answer: b) Infinite
Explanation: A plane mirror has an infinite focal length as its radius of curvature is also infinite.

21) The radius of curvature of a spherical mirror is:
a) Equal to its focal length
b) Twice its focal length
c) Half its focal length
d) Independent of its focal length
Answer: b) Twice its focal length
Explanation: The radius of curvature (R) is related to the focal length (f) by R=2f

22) A ray of light passing through the focus of a concave mirror:
a) Emerges parallel to the principal axis after reflection
b) Passes through the pole
c) Reflects back through the center of curvature
d) Remains unchanged
Answer: a) Emerges parallel to the principal axis after reflection
Explanation: A ray passing through the focus of a concave mirror reflects parallel to the principal axis.

23) What happens to the speed of light when it enters a denser medium?
a) Increases
b) Decreases
c) Remains the same
d) Becomes infinite
Answer: b) Decreases
Explanation: Light slows down when it enters a denser medium due to increased optical density.

24) Which mirror can form both real and virtual images?
a) Plane mirror
b) Convex mirror
c) Concave mirror
d) Parabolic mirror
Answer: c) Concave mirror
Explanation: A concave mirror forms real images when the object is beyond the focus and virtual images when the object is between the pole and focus.

25) If the magnification of an image is -2, the image is:
a) Real, inverted, and twice the size of the object
b) Virtual, erect, and twice the size of the object
c) Real, erect, and the same size as the object
d) Virtual, inverted, and the same size as the object
Answer: a) Real, inverted, and twice the size of the object
Explanation: A negative magnification indicates a real, inverted image. The value "2" means the image is twice the size of the object.

26) When light passes from water to air, the refractive index is expressed as:
a) $n_{water} / n_{air}$
b) $n_{air} / n_{water}$
c) $v_{air} / v_{water}$
d) $c / n_{water}$
Answer: b) $n_{air} / n_{water}$
Explanation: The refractive index is given as the ratio of the speed of light in air ( $n_{air}$ ) to the speed of light in water ( $n_{water}$ ).

27) If an object is placed at the focus of a convex lens, the image formed is:
a) Real, inverted, and the same size
b) Real, inverted, and highly enlarged
c) Virtual, erect, and diminished
d) Real, erect, and diminished
Answer: b) Real, inverted, and highly enlarged
Explanation: When the object is at the focus of a convex lens, the image is formed at infinity, highly enlarged.

28) The power of a lens with a focal length of 50 cm is:
a) 0.5 D
b) 2 D
c) -2 D
d) -0.5 D
Answer: b) 2 D
Explanation: Power ( $P$ ) is calculated as $P = 100 / f, where$ $f$ is in cm. For $f = 50$ , $P = 100/50 = 2 D$

29) A concave lens always forms an image that is:
a) Real, inverted, and enlarged
b) Virtual, erect, and diminished
c) Real, erect, and diminished
d) Virtual, inverted, and enlarged
Answer: b) Virtual, erect, and diminished
Explanation: A concave lens forms a virtual, erect, and diminished image irrespective of the object's position.

30) What is the focal length of a convex lens with a power of -5 D?
a) -20 cm
b) 20 cm
c) -50 cm
d) 50 cm
Answer: a) -20 cm
Explanation: The focal length (fff) is given by f=100/P. For P=−5cm, f = 100/-5 = -20cm.

31) When light passes through a prism, it splits into its constituent colors due to:
a) Reflection
b) Dispersion
c) Refraction
d) Diffraction
Answer: b) Dispersion
Explanation: Dispersion occurs when light separates into its constituent colors because different wavelengths refract at different angles.

32) The mirror formula is expressed as:
a) $1/v + 1/u = 1/f$
b) $1/v - 1/u = 1/f$
c) $v + u = f$
d) $u - v = f$
Answer: b) $1/v - 1/u = 1/f$
Explanation: The mirror formula relates the image distance (v), object distance (
$u$ ), and focal length ( $f$ ).
33) Which lens is used to correct hypermetropia (long-sightedness)?
a) Concave lens
b) Convex lens
c) Cylindrical lens
d) Plane lens
Answer: b) Convex lens
Explanation: A convex lens converges light rays, allowing the image to form on the retina for a hypermetropic eye.

34) The refractive index of glass is 1.5. What does this mean?
a) Light travels 1.5 times faster in glass than in air.
b) Light travels 1.5 times faster in air than in glass.
c) Light travels 1.5 times slower in air than in glass.
d) Glass reflects light completely.
Answer: b) Light travels 1.5 times faster in air than in glass.
Explanation: A refractive index of 1.5 indicates that light slows down by 1.5 times when entering glass from air.

35) Which image is formed by a plane mirror?
a) Virtual, inverted, and magnified
b) Virtual, erect, and same size as the object
c) Real, inverted, and diminished
d) Real, erect, and magnified
Answer: b) Virtual, erect, and same size as the object
Explanation: A plane mirror always forms a virtual, erect, and same-sized image.

36) Which of the following quantities changes during refraction of light?
a) Frequency
b) Speed
c) Wavelength
d) Both speed and wavelength
Answer: d) Both speed and wavelength
Explanation: During refraction, the speed and wavelength of light change, while the frequency remains constant.

37) What happens to the image distance as the object is moved closer to a convex lens?
a) Image distance increases.
b) Image distance decreases.
c) Image distance remains constant.
d) The image distance becomes infinite.
Answer: a) Image distance increases.
Explanation: As the object approaches the lens, the image distance increases and eventually becomes infinite at the focus.

38) What is the relationship between the angle of incidence and the angle of reflection?
a) Angle of reflection is always greater.
b) Angle of reflection is always smaller.
c) Angle of incidence equals angle of reflection.
d) Both angles are unrelated.
Answer: c) Angle of incidence equals angle of reflection.
Explanation: According to the first law of reflection, the angle of incidence is equal to the angle of reflection.

39) A concave mirror forms a real and inverted image when the object is placed:
a) Between the focus and the pole
b) At the focus
c) Beyond the focus
d) At infinity
Answer: c) Beyond the focus
Explanation: A concave mirror forms real and inverted images when the object is beyond the focus.

40) If the refractive index of medium A with respect to B is 2, then the refractive index of B with respect to A is:
a) 2
b) 1/2
c) 1
d) 4
Answer: b) 1/2
Explanation: Refractive index is reciprocal, so if
$n_{A/B} = 2$ , then $n_{B / A} = 1 / 2$

41) What is the SI unit of the power of a lens?
a) Meter
b) Dioptre
c) Hertz
d) Watt
Answer: b) Dioptre
Explanation: The power of a lens is measured in dioptres, defined as the reciprocal of the focal length in meters.

42) A convex mirror is used as a rear-view mirror because it:
a) Provides an enlarged image
b) Provides a diminished, erect, and wide field of view
c) Always forms a real image
d) Reduces the intensity of light
Answer: b) Provides a diminished, erect, and wide field of view
Explanation: Convex mirrors provide a wider field of view, which is ideal for rear-view mirrors.

43) Which of the following statements is true for the refractive index?
a) It is the ratio of the angle of incidence to the angle of refraction.
b) It depends on the color of light.
c) It has no relation to the speed of light.
d) It is always greater than 1.
Answer: b) It depends on the color of light.
Explanation: Refractive index varies with wavelength, causing dispersion when light passes through a prism.

44) The focal length of a concave mirror is:
a) Positive
b) Negative
c) Zero
d) Infinite
Answer: b) Negative
Explanation: The focal length of a concave mirror is negative as it is measured on the same side as the reflecting surface.

45) What is the relationship between the object distance (uuu) and the image distance (v) in a convex mirror?
a) $u > v$
b) $u = v$
c) $u < v$
d) Cannot be determined
Answer: a) $u > v$
Explanation: In a convex mirror, the image is always virtual, erect, and diminished, so the image distance is smaller than the object distance.

46) In refraction, the incident ray, refracted ray, and normal all lie:
a) Perpendicular to each other
b) On different planes
c) In the same plane
d) Parallel to each other
Answer: c) In the same plane
Explanation: According to the laws of refraction, the incident ray, refracted ray, and normal lie in the same plane.

47) If the object is at infinity, a convex lens forms an image that is:
a) Virtual and diminished
b) Real, inverted, and highly diminished at the focus
c) Virtual, inverted, and magnified
d) Real and enlarged
Answer: b) Real, inverted, and highly diminished at the focus
Explanation: When the object is at infinity, the image is formed at the focus of the lens, highly diminished.

48) Which phenomenon causes the apparent bending of a stick in water?
a) Reflection
b) Refraction
c) Dispersion
d) Total internal reflection
Answer: b) Refraction
Explanation: Refraction causes the light rays from the submerged part of the stick to bend, creating the illusion of a bent stick.

49) The critical angle for a medium depends on:
a) The speed of light in the medium
b) The angle of incidence
c) The refractive index of the medium
d) Both the speed of light and refractive index
Answer: d) Both the speed of light and refractive index
Explanation: The critical angle is determined by the refractive index, which is related to the speed of light in the medium.

50) What is the mirror formula?
a) $f = u + v$
b) $1/v + 1/u = 1/f$
c) $u - v = f$
d) $v - u = f$
$1/v + 1/u = 1/f$

51) The magnification of an object placed at 2F in front of a convex lens is:
a) 1
b) 2
c) -1
d) 0.5
Answer: a) 1
Explanation: When an object is placed at 2F, the image is formed at 2F on the other side, and the magnification is 1.

52) If the refractive index of water is 1.33, then the speed of light in water is:
a) $3 \times 10^8 \, \text{m/s}$
b) $1.33 \times 10^8 \, \text{m/s}$
c) $2.25 \times 10^8 \, \text{m/s}$
d) $3.99 \times 10^8 \, \text{m/s}$
Answer: c) $2.25 \times 10^8 \, \text{m/s}$

Explanation:Explanation: The speed of light in water is calculated as
$v = c/n$ . For $n = 1.33$ , $v = 3 \times 10^8 / 1.33 \approx 2.25 \times 10^8 \, \text{m/s}$

53) Which lens is thicker at the center than at the edges?
a) Concave lens
b) Convex lens
c) Cylindrical lens
d) Plane lens
Answer: b) Convex lens
Explanation: A convex lens is thicker at the center, causing light rays to converge.

54) The distance between the pole and the principal focus of a spherical mirror is called:
a) Radius of curvature
b) Focal length
c) Principal axis
d) Aperture
Answer: b) Focal length
Explanation: The focal length is the distance from the pole of the mirror to its principal focus.

55) A light ray passing through the optical center of a lens:
a) Deviates significantly
b) Passes through without deviation
c) Reflects back
d) Stops at the optical center
Answer: b) Passes through without deviation
Explanation: A ray passing through the optical center of a lens continues in a straight line without deviation.

56) In which mirror is the image always virtual, erect, and diminished?
a) Plane mirror
b) Concave mirror
c) Convex mirror
d) Parabolic mirror
Answer: c) Convex mirror
Explanation: A convex mirror always forms a virtual, erect, and diminished image irrespective of object distance.

57) The ability of a lens to converge or diverge light is called:
a) Refraction
b) Magnification
c) Power of the lens
d) Dispersion
Answer: c) Power of the lens
Explanation: The power of a lens measures its ability to bend light and is expressed in dioptres.

58) The focal length of a plane mirror is:
a) Zero
b) Positive
c) Negative
d) Infinite
Answer: d) Infinite
Explanation: A plane mirror has no curvature, so its focal length is considered infinite.

59) When an object is placed at the center of curvature of a concave mirror, the image formed is:
a) Real, inverted, and the same size as the object
b) Virtual, erect, and diminished
c) Real, inverted, and enlarged
d) Virtual, erect, and magnified
Answer: a) Real, inverted, and the same size as the object
Explanation: At the center of curvature, the image is real, inverted, and of the same size as the object.

60) Which phenomenon allows optical fibers to transmit light efficiently?
a) Reflection
b) Refraction
c) Total internal reflection
d) Dispersion
Answer: c) Total internal reflection
Explanation: Optical fibers rely on total internal reflection to guide light through their structure without loss.

MCQs from the exercise part of the chapter

1) Which one of the following materials cannot be used to make a lens?

a) Water
b) Glass
c) Plastic
d) Clay

Answer: d) Clay
Explanation: Clay is an opaque material and cannot transmit light, making it unsuitable for lens-making.

2) The image formed by a concave mirror is observed to be virtual, erect, and larger than the object. Where should the position of the object be?

a) Between the principal focus and the center of curvature
b) At the center of curvature
c) Beyond the center of curvature
d) Between the pole of the mirror and its principal focus

Answer: d) Between the pole of the mirror and its principal focus
Explanation: When an object is placed between the pole and focus of a concave mirror, the image is virtual, erect, and magnified.

3) Where should an object be placed in front of a convex lens to get a real image of the same size as the object?

a) At the principal focus of the lens
b) At twice the focal length
c) At infinity
d) Between the optical center of the lens and its principal focus

Answer: b) At twice the focal length
Explanation: A real image of the same size is formed by a convex lens when the object is placed at $2F$ , and the image is also formed at $2 F on the opposite site.$

4) A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be:

a) Both concave
b) Both convex
c) The mirror is concave, and the lens is convex
d) The mirror is convex, and the lens is concave

Answer: a) Both concave
Explanation: A negative focal length indicates that both the mirror and the lens are concave.

5) No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be:

a) Only plane
b) Only concave
c) Only convex
d) Either plane or convex

Answer: d) Either plane or convex
Explanation: Plane mirrors and convex mirrors always form erect images, irrespective of the object's distance.

6) Which of the following lenses would you prefer to use while reading small letters found in a dictionary?

a) A convex lens of focal length 50 cm
b) A concave lens of focal length 50 cm
c) A convex lens of focal length 5 cm
d) A concave lens of focal length 5 cm

Answer: c) A convex lens of focal length 5 cm
Explanation: A convex lens with a short focal length provides the required magnification to read small letters.

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