Assertion and Reason Questions Chapter-9 Ray Optics and Optical Instruments
Assertion (A) and other labelled Reason (R). Select the correct answer to these
questions from the options as 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.
1. Assertion (A): The angle of incidence is always equal to the angle of
reflection.
Reason (R): This is a fundamental property of reflection.
2. Assertion (A): A concave lens is also known as a diverging lens.
Reason (R): Concave lenses cause parallel rays of light to
converge at a point.
3. Assertion (A): The focal length of a convex lens is positive.
Reason (R): Convex lenses converge light rays to a point on the
opposite side of the lens.
4. Assertion (A): The power of a lens is defined as the reciprocal of its focal
length.
Reason (R): Power is measured in diopters, which is the unit of
focal length.
5. Assertion (A): Total internal reflection can occur only when light travels
from a denser to a rarer medium.
Reason (R): Total internal reflection occurs at angles greater
than the critical angle.
6. Assertion (A): A virtual image cannot be projected on a screen.
Reason (R): A virtual image is formed by rays that do not actually
converge.
7. Assertion (A): The focal length of a concave lens is negative.
Reason (R): A concave lens causes parallel rays of light to
diverge.
8. Assertion (A): Light behaves as a particle and a wave in different
situations.
Reason (R): This dual nature is responsible for phenomena such as
diffraction and photoelectric effect.
9. Assertion (A): The image formed by a convex mirror is always virtual.
Reason (R): Convex mirrors always diverge light rays.
10. Assertion (A): The focal length of a plane mirror is infinity.
Reason (R): Light rays reflected from a plane mirror do not
converge or diverge.
11. Assertion (A): In a microscope, the objective lens has a short focal length.
Reason (R): Short focal lengths are needed to magnify small
objects.
12. Assertion (A): Lenses are classified into two main categories: convex and
concave.
Reason (R): This classification is based on their shape and the
way they bend light.
13. Assertion (A): A Ray diagram can be used to locate the position of an image
formed by a lens.
Reason (R): Ray diagrams show the path of light rays through
optical devices.
14. Assertion (A): The angle of deviation is maximum for a prism at the critical
angle.
Reason (R): Total internal reflection occurs at angles greater
than the critical angle.
15. Assertion (A): A ray of light passes through the center of curvature of a
spherical mirror without changing its direction.
Reason (R): The center of curvature is a point on the principal
axis of the mirror.
16. Assertion (A): The image formed by a concave mirror can be real or virtual.
Reason (R): The nature of the image depends on the position of the
object relative to the focal point.
17. Assertion (A): The distance of the object and the image from the optical
center of a lens are related by the lens formula.
Reason (R): The lens formula describes the relationship between
object distance, image distance, and focal length.
18. Assertion (A): An optical fiber transmits light through total internal
reflection.
Reason (R): This principle allows for the efficient transfer of
light over long distances.
19. Assertion (A): The brightness of an image depends on the size of the
aperture of the lens.
Reason (R): A larger aperture allows more light to enter the lens,
increasing brightness.
20. Assertion (A): In a simple microscope, the image is always virtual.
Reason (R): Virtual images appear on the same side as the object.
21. Assertion (A): A larger focal length in a lens results in a lower
magnification.
Reason (R): Lower magnification occurs due to less bending of
light rays.
22. Assertion (A): The critical angle for total internal reflection is dependent
on the medium.
Reason (R): The critical angle is calculated based on the
refractive indices of the two media.
23. Assertion (A): The formula for finding the position of the image in a convex
lens is 1/f = 1/v - 1/u.
Reason (R): This is derived from the properties of light
refraction in lenses.
24. Assertion (A): The speed of light is different in different media.
Reason (R): The refractive index of a medium is defined as the
ratio of the speed of light in vacuum to the speed of light in the medium.
25. Assertion (A): A rainbow is formed due to the refraction of light in water
droplets.
Reason (R): Light refracts, reflects, and disperses in the
droplets to create a spectrum.
26. Assertion (A): The principal focus of a concave mirror is located in front
of the mirror.
Reason (R): The principal focus is the point where rays parallel
to the principal axis converge.
27. Assertion (A): The focal length of a convex lens is equal to the distance
from the lens to its focal point.
Reason (R): The focal point is where light rays converge after
passing through the lens.
28. Assertion (A): Lenses can cause chromatic aberration.
Reason (R): Different wavelengths of light refract at different
angles in a lens.
29. Assertion (A): The power of a lens is the ability to converge or diverge
light.
Reason (R): Power is calculated as the inverse of the focal
length.
30. Assertion (A): A convex lens can form both real and virtual images.
Reason (R): The type of image formed depends on the object
distance relative to the focal length.
31. Assertion (A): The angle of incidence is always less than the angle of
refraction when light travels from air to glass.
Reason (R): Light slows down when entering a denser medium,
bending toward the normal.
32. Assertion (A): The distance from the optical center to the principal focus
of a lens is called its focal length.
Reason (R): Focal length is a key parameter in defining the
optical properties of a lens.
33. Assertion (A): The critical angle is larger for denser media compared to
rarer media.
Reason (R): A larger critical angle indicates a greater degree of
bending of light rays.
34. Assertion (A): The image formed by a plane mirror is always upright.
Reason (R): An upright image is formed due to the normal incidence
of light rays.
35. Assertion (A): A lens that is thicker in the middle than at the edges is a
concave lens.
Reason (R): A concave lens diverges light rays.
36. Assertion (A): Light travels faster in a vacuum than in any medium.
Reason (R): The speed of light in a medium is always less than its
speed in a vacuum.
37. Assertion (A): The image distance is negative for virtual images formed by a
concave lens.
Reason (R): The convention for image distance is that negative
values indicate virtual images.
38. Assertion (A): The focal length of a convex lens increases with an increase
in the radius of curvature.
Reason (R): A larger radius of curvature results in a flatter lens
profile.
39. Assertion (A): The position of the image formed by a concave lens can be
determined using the lens formula.
Reason (R): The lens formula applies to both convex and concave
lenses.
40. Assertion (A): A ray of light parallel to the principal axis will pass
through the focal point after refraction through a convex lens.
Reason (R): This is due to the converging nature of a convex lens.
41. Assertion (A): A virtual image can be projected onto a screen.
Reason (R): Virtual images are formed by diverging rays.
42. Assertion (A): The magnification produced by a lens is defined as the ratio
of the height of the image to the height of the object.
Reason (R): Magnification can be greater than one.
43. Assertion (A): The distance between two consecutive bright fringes in an
interference pattern is called fringe width.
Reason (R): Fringe width is dependent on the wavelength of light
used.
44. Assertion (A): The power of a lens is positive for a convex lens.
Reason (R): Convex lenses converge light, giving them positive
focal lengths.
45. Assertion (A): The image formed by a concave mirror can be real or virtual
depending on the object position.
Reason (R): The type of image formed is always real when the
object is beyond the center of curvature.
46. Assertion (A): The radius of curvature of a lens is always positive for a
converging lens.
Reason (R): The convention assigns positive values to converging
lenses.
47. Assertion (A): Light rays passing through the focal point of a concave lens
diverge after refraction.
Reason (R): Concave lenses always cause rays to diverge,
regardless of their initial direction.
48. Assertion (A): Total internal reflection can occur when light travels from a
denser medium to a rarer medium.
Reason (R): The angle of incidence must exceed the critical angle
for total internal reflection.
49. Assertion (A): The focal point of a lens can be determined experimentally
using a distant light source.
Reason (R): Light rays from a distant source are parallel,
allowing for easy measurement of the focal length.
50. Assertion (A): An increase in the refractive index of a medium leads to a
decrease in the speed of light within that medium.
Reason (R): The refractive index is defined as the ratio of the
speed of light in vacuum to that in the medium.