LIGHT, Class X Physics Assertion and Reason Question

  

Assertion and Reason Questions for Class 10 Science Chapter 10 Light-Reflection and Refraction



The following questions consist of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Q.1.                                                                                                                                           Assertion(A): The centre of curvature is not a part of the mirror. It lies outside its reflecting surface.
Reason (R): The reflecting surface of a spherical mirror forms a part of a sphere. This sphere has a centre.                                                                                                                                                Answer (a)

Q.2.                                                                                                                                                     Assertion (A): A ray passing through the centre of curvature of a concave mirror after reflection, is reflected back along the same path.
Reason (R): The incident rays fall on the mirror along the normal to the reflecting surface.         Answer (a)

Q.3.                                                                                                                                                 Assertion (A): Light does not travel in the same direction in all the media.
Reason (R): The speed of light does not change as it enters from one transparent medium to another. Answer (c)

Q.4.                                                                                                                                           Assertion(A): The emergent ray is parallel to the direction of the incident ray.
Reason (R): The extent of bending of the ray of light at the opposite parallel faces (air-glass interface and glass-air interface) of the rectangular glass slab is equal and opposite.                                                 Answer (a)

Q.5.                                                                                                                                           Assertion(A): A ray of light traveling from a rarer medium to a denser medium slows down and bends away from the normal. When it travels from a denser medium to a rarer medium, it speeds up and bends towards the normal.
Reason (R): The speed of light is higher in a rarer medium than in a denser medium.                  Answer (d)

Q.6.                                                                                                                                   Assertion(A): The mirrors used in searchlights are concave spherical.
Reason (R): In a concave spherical mirror the image formed is always virtual.                              Answer (c)

Q.7.                                                                                                                                  Assertion(A): Light travels faster in glass than in air.
Reason (R): Glass is denser than air.                                                                                               Answer (d)

Q.8.                                                                                                                                                 Assertion(A): The driver mirror is a convex mirror for observing traffic at the back.
Reason (R): A convex mirror has a much larger field of view than a plane mirror.                        Answer  (a)

Q.9.                                                                                                                                  Assertion(A): The mirror formula can be applied to a plane mirror.
Reason (R): A plane mirror is a spherical mirror of infinite focal length.                                         Answer (a)

Q.10.                                                                                                                                         Assertion(A): It is not possible to see a virtual image by eye.
Reason (R): The rays that seem to emanate from a virtual image do not in fact emanates from the image.                                                                                                                                                            Answer (d)

Q.11.                                                                                                                                         Assertion(A): When the object moves with a velocity of 2 m/s, its image in the plane mirror moves with a velocity of 4 m/s.
Reason (R): The image formed by a plane mirror is as far behind the mirror as the object is in front of it.                                                                                                                                                       Answer (a)

Q.12.                                                                                                                                         Assertion(A): The height of an object is always considered positive.
Reason (R): An object is always placed above the principal axis in this upward direction.           Answer (a)

Q.13.                                                                                                                                         Assertion(A): Concave mirrors are used as make-up mirrors.
Reason (R): When the face is held within the focus of a concave mirror, then a diminished image of the face is seen in the concave mirror.                                                                                                    Answer (c)

Q.14.                                                                                                                                         Assertion(A): Refractive index has no units.
Reason (R): The refractive index is a ratio of two similar quantities.                                              Answer (a)

Q.15.                                                                                                                                         Assertion(A): The formula connecting u, v, and f for a spherical mirror is valid in all situations for all spherical mirrors for all positions of the object.
Reason (R): Laws of reflection are strictly valid for plane surfaces.                                              Answer (c)

Q.16.                                                                                                                                    Assertion(A): A person cannot see his image in a concave mirror, unless, he is standing beyond the center of curvature of the mirror.
Reason (R): In a concave mirror, an image formed is real provided the object is situated beyond its focus.                                                                                                                                                Answer (b)

Q.17.                                                                                                                           Assertion(A): Virtual images are always erect.
Reason (R): Virtual images are formed by diverging lenses only.                                                  Answer (c)

Q.18.                                                                                                                                             Assertion: If a ray of light is incident on a convex mirror along its principal axis, then the angle of incidence as well as the angle of reflection for a ray of light will be zero.                                    Reason: A ray of light going towards the centre of curvature of a convex mirror is reflected back along the same path.                                                                                                                                  Answer. (b)

Q 19.                                                                                                                                             Assertion: Linear magnification of a mirror has no unit.                                                              Reason: The ratio of the height of the image to the height of the object is the linear magnification produced by a mirror.                                                                                                                       Answer. (a): Linear magnification of a mirror is the ratio of the height of the image (cm) and the height of the object (cm) and it has no unit.                                                                                               

Q 20.                                                                                                                                             Assertion: In the case of a concave mirror, the minimum distance between a real object and its real image is zero.                                                                                                                                      Reason: If a concave mirror forms a virtual image of the real object, the image is magnified.                  Answer. (b): If an object is placed at the center of curvature of a concave mirror, its image is at the centre of curvature. Thus, the minimum distance between an object and its real image is zero. If an object is between the pole and the focus of the concave mirror, its image is virtual and magnified.

Q 21.                                                                                                                                             Assertion: The size of the mirror affects the nature of the image.                                                            Reason: Small mirrors always form virtual images.                                                                         Answer. (d): The size of the image does not affect the nature of the image except that a bigger image gathers more light rays due to a wider aperture.

Q 22.                                                                                                                                             Assertion: Keeping a point object fixed, if a plane mirror is moved, the image will also move.   Reason: In the case of a plane mirror, the distance between an object and its image is equal from any point on the mirror.                                                                                                                          Answer. (a): The image formed in a plane mirror is at the same distance behind the mirror as the object is in the front of the mirror. The image and the object are at equal distances from a plane mirror.

Q 23.                                                                                                                                              Assertion (A): A ray of light passing through the centre of curvature of a spherical mirror retraces its path after reflection from the mirror.                                                                                                 Reason (R): A ray of light passing through the centre of curvature of a spherical mirror is incident normally on the surface of the mirror.                                                                                             Answer. (a)

Q 24.                                                                                                                                                     Assertion (A): Glass is optically denser than water.                                                                         Reason (R): An optically denser medium is one in which the speed of light is comparatively less.  Answer. (a)

Q 25.                                                                                                                                              Assertion (A): Magnification of a real image is negative but magnification of a virtual image is positive.                                                                                                                                             Reason (R): The real image is inverted but the virtual image is erect.                                         Answer. (a)

Q 26.                                                                                                                                              Assertion (A): A convex lens forms a virtual, erect, and enlarged image of an object situated between the lens and its principal focus.                                                                                                                     Reason (R): A convex lens is a diverging lens.                                                                              Answer. (c)

Q 27.                                                                                                                                              Assertion (A): The SI unit of refractive index is ms-1.                                                                                Reason (R): Glass is said to be optically denser than kerosene because the optical density of glass is greater than that of kerosene.                                                                                                           Answer. (d)

Q 28.                                                                                                                                              Assertion (A): A convex lens is called a convergent lens but a concave lens acts as a divergent lens.      Reason (R): A convergent lens is that which always forms a real image of a real object and a divergent lens is that which can never form a real image.                                                                               Answer. (c)

Q 29.                                                                                                                                                Assertion (A): The speed of light in water is 2.25 × 108 ms1.                                                                    Reason (R): The refractive index of water is 4/3.                                                                                         Answer. (a)

Q 30.                                                                                                                                              Assertion (A): The distance of a real image formed by a mirror is taken to be negative but for a lens, we take it with a positive sign.                                                                                                                      Reason (R): A mirror forms a real image of an object in front of it but a real image formed by a lens lies on the other side of the lens.                                                                                                                  Answer. (a)

Q 31.                                                                                                                                                              Assertion (A): Large-sized concave mirrors are used to concentrate thermal radiation in solar furnaces.
Reason (R): A convex mirror is fitted in automobiles to increase the field of view of the vehicle driver.  Answer. (b)

 

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