1. Light travels in —
A) Curved line
B) Straight line
C) Zig-zag path
D) Random direction
Answer: B) Straight line
Explanation: Light travels in a straight line in a homogeneous medium. This is known as rectilinear propagation of light.
2. The speed of light in vacuum is approximately —
A) 3×1063 \times 10^63×106 m/s
B) 3×1083 \times 10^83×108 m/s
C) 3×1053 \times 10^53×105 m/s
D) 3×10103 \times 10^{10}3×1010 m/s
Answer: B) 3×1083 \times 10^83×108 m/s
Explanation: The speed of light in vacuum (or air approximately) is 2.998×1082.998 \times 10^82.998×108 m/s.
3. Which phenomenon shows that light travels in a straight line?
A) Reflection
B) Refraction
C) Shadow formation
D) Dispersion
Answer: C) Shadow formation
Explanation: The formation of shadows occurs because light travels in straight lines and cannot bend around opaque objects.
4. The bending of light when it passes from one medium to another is called —
A) Reflection
B) Refraction
C) Dispersion
D) Scattering
Answer: B) Refraction
Explanation: Refraction is the change in direction of light when it passes from one medium to another due to change in its speed.
5. The mirror which gives the widest field of view is —
A) Plane mirror
B) Concave mirror
C) Convex mirror
D) Parabolic mirror
Answer: C) Convex mirror
Explanation: Convex mirrors diverge light and give a wide field of view; hence used in vehicles as rear-view mirrors.
6. The image formed by a plane mirror is —
A) Real and inverted
B) Virtual and erect
C) Real and erect
D) Virtual and inverted
Answer: B) Virtual and erect
Explanation: Plane mirrors always form virtual, erect, and laterally inverted images.
7. The focal length of a plane mirror is —
A) Infinite
B) Zero
C) Equal to radius of curvature
D) Half of radius of curvature
Answer: A) Infinite
Explanation: Since a plane mirror has no curvature, its radius of curvature and hence focal length are infinite.
8. The lens which is thicker at the centre than at the edges is called —
A) Concave lens
B) Convex lens
C) Cylindrical lens
D) Plano lens
Answer: B) Convex lens
Explanation: A convex lens converges light rays; it is thicker at the centre and thinner at the edges.
9. Which type of mirror is used by dentists to see enlarged images of teeth?
A) Plane mirror
B) Convex mirror
C) Concave mirror
D) Spherical mirror
Answer: C) Concave mirror
Explanation: Concave mirrors produce a magnified image of nearby objects, hence used by dentists.
10. The image formed on the retina of the human eye is —
A) Real and inverted
B) Virtual and erect
C) Real and erect
D) Virtual and inverted
Answer: A) Real and inverted
Explanation: The eye lens focuses light rays on the retina, forming a real and inverted image.
11. Which color of light deviates the least in a prism?
A) Red
B) Blue
C) Violet
D) Green
Answer: A) Red
Explanation: Red light has the longest wavelength and hence deviates least during dispersion.
12. The splitting of white light into seven colors is called —
A) Reflection
B) Refraction
C) Dispersion
D) Diffraction
Answer: C) Dispersion
Explanation: Dispersion occurs due to the different refractive indices for different wavelengths in a prism.
13. Which part of the eye controls the amount of light entering it?
A) Cornea
B) Lens
C) Iris
D) Retina
Answer: C) Iris
Explanation: The iris adjusts the pupil size to regulate the amount of light entering the eye.
14. The power of a lens is measured in —
A) Watts
B) Meters
C) Diopters
D) Candela
Answer: C) Diopters
Explanation: Lens power (P) = 1 / focal length (in meters). Its unit is diopter (D).
15. The phenomenon responsible for the twinkling of stars is —
A) Reflection
B) Refraction of light through air layers
C) Dispersion
D) Diffraction
Answer: B) Refraction of light through air layers
Explanation: The changing air density refracts starlight differently, making stars appear to twinkle.
16. The color of the sky appears blue due to —
A) Reflection
B) Refraction
C) Scattering
D) Absorption
Answer: C) Scattering
Explanation: Blue light is scattered more by air molecules (Rayleigh scattering), giving the sky its blue color.
17. The instrument used to see distant objects clearly is —
A) Microscope
B) Telescope
C) Periscope
D) Binoculars
Answer: B) Telescope
Explanation: Telescopes use lenses or mirrors to collect and magnify light from distant objects.
18. The phenomenon of reflection from smooth surfaces is called —
A) Diffuse reflection
B) Regular reflection
C) Irregular reflection
D) Random reflection
Answer: B) Regular reflection
Explanation: Smooth surfaces reflect light in one direction, causing regular reflection and clear images.
19. Which type of lens is used to correct myopia (short-sightedness)?
A) Convex lens
B) Concave lens
C) Cylindrical lens
D) Plano lens
Answer: B) Concave lens
Explanation: Concave lenses diverge light rays and help focus them on the retina for myopic eyes.
20. Which device uses the principle of total internal reflection?
A) Telescope
B) Microscope
C) Optical fiber
D) Camera
Answer: C) Optical fiber
Explanation: Optical fibers transmit light through total internal reflection for communication and medical imaging.
21. The phenomenon of light bending around obstacles is called —
A) Reflection
B) Refraction
C) Diffraction
D) Dispersion
Answer: C) Diffraction
Explanation: Diffraction is the bending of light waves around the edges of an obstacle or slit.
22. The speed of light is maximum in —
A) Glass
B) Water
C) Air
D) Vacuum
Answer: D) Vacuum
Explanation: Light travels fastest in vacuum since there are no particles to interact with the light.
23. Which of the following can show total internal reflection?
A) Air to glass
B) Water to air
C) Glass to air
D) Both B and C
Answer: D) Both B and C
Explanation: Total internal reflection occurs when light travels from a denser to a rarer medium (like glass to air or water to air) at an angle greater than the critical angle.
24. Which mirror is used in vehicle headlights?
A) Plane mirror
B) Convex mirror
C) Concave mirror
D) Spherical mirror
Answer: C) Concave mirror
Explanation: Concave mirrors converge light rays to produce a strong, parallel beam, useful for headlights.
25. The color of an object depends on —
A) Its shape
B) Its size
C) The light it reflects
D) The light it absorbs
Answer: C) The light it reflects
Explanation: The color we see is due to the wavelengths of light reflected by the object.
26. The unit of refractive index is —
A) m/s
B) No unit (dimensionless)
C) Newton
D) Diopter
Answer: B) No unit (dimensionless)
Explanation: Refractive index is a ratio of two speeds of light (in vacuum and in medium), hence it has no unit.
27. A rainbow is formed due to —
A) Reflection
B) Refraction and dispersion
C) Diffraction
D) Polarization
Answer: B) Refraction and dispersion
Explanation: Raindrops act like small prisms, refracting and dispersing sunlight into colors, forming a rainbow.
28. The mirror formula is —
A) 1f=1u−1v\frac{1}{f} = \frac{1}{u} – \frac{1}{v}f1=u1−v1
B) 1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}f1=v1+u1
C) 1u=1v−1f\frac{1}{u} = \frac{1}{v} – \frac{1}{f}u1=v1−f1
D) f=uvf = uvf=uv
Answer: B) 1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}f1=v1+u1
Explanation: The mirror formula relates the focal length (f), image distance (v), and object distance (u).
29. The lens which is thinner at the center than at the edges is —
A) Convex lens
B) Concave lens
C) Cylindrical lens
D) Plano lens
Answer: B) Concave lens
Explanation: Concave lenses diverge light rays and are thinner at the center than at the edges.
30. Which color of light has the shortest wavelength?
A) Red
B) Violet
C) Blue
D) Green
Answer: B) Violet
Explanation: Violet light has the shortest wavelength (~400 nm) and highest frequency among visible light.
31. The device used to produce parallel rays of light is —
A) Lens
B) Mirror
C) Collimator
D) Prism
Answer: C) Collimator
Explanation: A collimator aligns light rays parallel to each other, used in optical instruments.
32. The refractive index of glass is approximately —
A) 1.33
B) 1.44
C) 1.52
D) 1.00
Answer: C) 1.52
Explanation: The refractive index of common crown glass is around 1.52, meaning light slows down in glass.
33. The image formed by a concave mirror when the object is at the center of curvature is —
A) Real, inverted, same size
B) Virtual, erect, magnified
C) Real, erect, smaller
D) Virtual, inverted, smaller
Answer: A) Real, inverted, same size
Explanation: For an object at the center of curvature, the image forms at the same point, real and inverted.
34. Which phenomenon is used in optical fibers?
A) Diffraction
B) Total internal reflection
C) Scattering
D) Refraction
Answer: B) Total internal reflection
Explanation: Light signals travel inside optical fibers through continuous total internal reflection.
35. The focal length of a lens is +20 cm. The lens is —
A) Convex
B) Concave
C) Plano-concave
D) Cylindrical
Answer: A) Convex
Explanation: Positive focal length indicates a converging (convex) lens; concave lenses have negative focal length.
36. Which of the following is a divergent lens?
A) Convex lens
B) Plano-convex lens
C) Concave lens
D) Double convex lens
Answer: C) Concave lens
Explanation: Concave lenses cause parallel rays to diverge, spreading outwards.
37. Which of the following statements is true about the image formed by convex mirrors?
A) Always real
B) Always virtual and erect
C) Sometimes real
D) Sometimes inverted
Answer: B) Always virtual and erect
Explanation: Convex mirrors always form virtual, erect, and diminished images, irrespective of object position.
38. The apparent bending of a stick partially immersed in water is due to —
A) Reflection
B) Refraction
C) Diffraction
D) Dispersion
Answer: B) Refraction
Explanation: The stick appears bent because light from the submerged part bends as it passes from water to air.
39. The brightness of light depends on —
A) Frequency
B) Amplitude
C) Wavelength
D) Speed
Answer: B) Amplitude
Explanation: The amplitude of a light wave determines its intensity or brightness.
40. What is the nature of the image formed by a concave mirror when the object is between the focus and the pole?
A) Real, inverted, magnified
B) Virtual, erect, magnified
C) Real, erect, same size
D) Virtual, inverted, diminished
Answer: B) Virtual, erect, magnified
Explanation: When the object lies between the focus and pole of a concave mirror, a virtual and magnified image is formed behind the mirror.
41. The mirror used in solar furnaces is —
A) Plane mirror
B) Convex mirror
C) Concave mirror
D) Cylindrical mirror
Answer: C) Concave mirror
Explanation: Concave mirrors focus sunlight at a single point, producing high temperatures for solar furnaces.
42. Which color has the highest frequency?
A) Blue
B) Red
C) Green
D) Violet
Answer: D) Violet
Explanation: Violet has the shortest wavelength and highest frequency in the visible spectrum.
43. What type of image is formed by a convex lens when the object is between focus and optical center?
A) Real and inverted
B) Virtual and erect
C) Real and diminished
D) Real and magnified
Answer: B) Virtual and erect
Explanation: When the object is between focus and the optical center, the convex lens forms a virtual, erect, and magnified image.
44. The scattering of light by particles in its path is known as —
A) Reflection
B) Refraction
C) Scattering
D) Diffraction
Answer: C) Scattering
Explanation: Scattering is the deviation of light caused by dust or air molecules; it explains why the sky looks blue.
45. The power of a convex lens of focal length 0.5 m is —
A) +1 D
B) +2 D
C) +3 D
D) +4 D
Answer: B) +2 D
Explanation: Power P=1/f=1/0.5=+2 dioptersP = 1/f = 1/0.5 = +2 \, \text{diopters}P=1/f=1/0.5=+2diopters. Positive sign indicates a convex lens.
46. The refractive index of a medium depends on —
A) Color of light
B) Temperature
C) Nature of medium
D) All of the above
Answer: D) All of the above
Explanation: The refractive index varies with the wavelength (color), temperature, and density of the medium.
47. The type of image formed by a pinhole camera is —
A) Real and inverted
B) Virtual and erect
C) Real and erect
D) Virtual and inverted
Answer: A) Real and inverted
Explanation: A pinhole camera forms a real and inverted image on the screen.
48. The phenomenon used in the working of periscope is —
A) Refraction
B) Total internal reflection
C) Reflection
D) Diffraction
Answer: C) Reflection
Explanation: A periscope uses plane mirrors placed at 45° to reflect light twice, allowing observation over obstacles.
49. What happens to the speed of light when it enters a denser medium?
A) Increases
B) Decreases
C) Remains constant
D) Becomes infinite
Answer: B) Decreases
Explanation: Light slows down in denser media due to increased optical density.
50. The focal length of a concave mirror is —
A) Positive
B) Negative
C) Zero
D) Infinite
Answer: B) Negative
Explanation: By sign convention, the focal length of concave mirrors (which converge light) is taken as negative.
51. The phenomenon of seeing the sun before it rises and after it sets is due to —
A) Reflection
B) Refraction
C) Dispersion
D) Scattering
Answer: B) Refraction
Explanation: Atmospheric refraction bends sunlight, making the sun visible even when it is below the horizon.
52. The ability of the eye to focus on near and distant objects is called —
A) Power of vision
B) Accommodation
C) Convergence
D) Myopia
Answer: B) Accommodation
Explanation: The eye changes the focal length of its lens to view objects at different distances — this is accommodation.
53. The unit of luminous intensity is —
A) Lux
B) Lumen
C) Candela
D) Joule
Answer: C) Candela
Explanation: The SI unit of luminous intensity (brightness perceived by the eye) is candela (cd).
54. The critical angle for total internal reflection depends on —
A) Angle of incidence
B) Refractive index of medium
C) Wavelength of light
D) Both B and C
Answer: D) Both B and C
Explanation: The critical angle varies with the refractive index and wavelength of the light.
55. A real image can be obtained on a —
A) Plane mirror
B) Screen
C) Eye
D) None of these
Answer: B) Screen
Explanation: Real images are formed by actual intersection of light rays and can be projected onto a screen.
56. Which type of mirror is used in street lights?
A) Convex mirror
B) Concave mirror
C) Plane mirror
D) Parabolic mirror
Answer: D) Parabolic mirror
Explanation: Parabolic mirrors focus light into a powerful beam, making them ideal for streetlights and spotlights.
57. When white light passes through a prism, which color bends the most?
A) Red
B) Blue
C) Green
D) Violet
Answer: D) Violet
Explanation: Violet light has the shortest wavelength and hence bends (refracts) the most.
58. A concave mirror forms a virtual image when the object is placed —
A) Beyond the center of curvature
B) At infinity
C) Between the pole and focus
D) At the center of curvature
Answer: C) Between the pole and focus
Explanation: In this position, the concave mirror forms a virtual, erect, and magnified image behind the mirror.
59. The reflection from rough surfaces is called —
A) Diffused reflection
B) Regular reflection
C) Total reflection
D) Irregular refraction
Answer: A) Diffused reflection
Explanation: Rough surfaces reflect light irregularly, scattering it in many directions — this is diffused reflection.
60. The splitting of sunlight into its constituent colors by a prism is an example of —
A) Refraction
B) Dispersion
C) Scattering
D) Diffraction
Answer: B) Dispersion
Explanation: The prism separates white light into seven colors (VIBGYOR) due to different refractive indices for each color.
81. The mirror used in rear-view mirrors of vehicles is —
A) Plane mirror
B) Concave mirror
C) Convex mirror
D) Cylindrical mirror
Answer: C) Convex mirror
Explanation: Convex mirrors give a wide field of view and always produce virtual, erect, and diminished images.
82. The image formed by a concave mirror for an object placed at infinity is —
A) Real, inverted, and highly diminished
B) Virtual, erect, and magnified
C) Real, erect, and same size
D) Virtual, inverted, and same size
Answer: A) Real, inverted, and highly diminished
Explanation: Parallel rays from infinity converge at the focus, forming a real and highly diminished image.
83. The focal length of a lens depends on —
A) Shape of the lens
B) Material of the lens
C) Surrounding medium
D) All of the above
Answer: D) All of the above
Explanation: Focal length varies with curvature (shape), refractive index (material), and surrounding medium.
84. Which lens is used to correct hypermetropia (long-sightedness)?
A) Concave lens
B) Convex lens
C) Plano-concave lens
D) Cylindrical lens
Answer: B) Convex lens
Explanation: Hypermetropia is corrected using a convex lens that converges light rays before they enter the eye.
85. The time taken by light to travel from the Sun to Earth is approximately —
A) 1 minute
B) 8 minutes 20 seconds
C) 15 minutes
D) 24 minutes
Answer: B) 8 minutes 20 seconds
Explanation: Light takes about 500 seconds (~8.3 minutes) to travel 1.496 × 10⁸ km from the Sun to Earth.
86. Which type of mirror is used in searchlights?
A) Convex
B) Concave
C) Plane
D) Parabolic
Answer: B) Concave
Explanation: Concave mirrors produce a strong parallel beam of light when the source is at their focus.
87. The value of the critical angle for glass-air is approximately —
A) 30°
B) 42°
C) 60°
D) 75°
Answer: B) 42°
Explanation: For glass (n ≈ 1.52), the critical angle for total internal reflection is about 42°.
88. Which color of light is scattered the most in the atmosphere?
A) Red
B) Yellow
C) Blue
D) Green
Answer: C) Blue
Explanation: Blue light has a shorter wavelength and is scattered more by air molecules (Rayleigh scattering).
89. The rear-view mirror of a car forms an image which is —
A) Real, inverted, smaller
B) Virtual, erect, smaller
C) Real, erect, larger
D) Virtual, inverted, same size
Answer: B) Virtual, erect, smaller
Explanation: Convex mirrors used in rear-view mirrors always form virtual, erect, and diminished images.
90. The speed of light in glass is approximately —
A) 3×108 m/s3 \times 10^8 \, \text{m/s}3×108m/s
B) 2×108 m/s2 \times 10^8 \, \text{m/s}2×108m/s
C) 1.5×108 m/s1.5 \times 10^8 \, \text{m/s}1.5×108m/s
D) 1×108 m/s1 \times 10^8 \, \text{m/s}1×108m/s
Answer: B) 2×108 m/s2 \times 10^8 \, \text{m/s}2×108m/s
Explanation: Due to refraction, the speed of light decreases to about two-thirds of its speed in vacuum when in glass.
91. Which part of the human eye helps to focus light on the retina?
A) Cornea
B) Pupil
C) Lens
D) Iris
Answer: C) Lens
Explanation: The eye lens adjusts its curvature to focus light rays onto the retina.
92. Which phenomenon explains the formation of mirages?
A) Reflection
B) Refraction
C) Total internal reflection
D) Diffraction
Answer: C) Total internal reflection
Explanation: Mirages occur due to total internal reflection of light in layers of air with varying densities.
93. The human eye is most sensitive to which color?
A) Blue
B) Green
C) Red
D) Yellow
Answer: B) Green
Explanation: The human eye is most sensitive to green light (~555 nm) in the visible spectrum.
94. A simple microscope consists of —
A) One convex lens
B) Two convex lenses
C) One concave lens
D) One concave and one convex lens
Answer: A) One convex lens
Explanation: A simple microscope is made of a single convex lens used to magnify small objects.
95. The formation of images in a pinhole camera supports which property of light?
A) Diffraction
B) Rectilinear propagation
C) Scattering
D) Reflection
Answer: B) Rectilinear propagation
Explanation: The straight-line travel of light enables the formation of an inverted image in a pinhole camera.
96. The color of the sky appears red during sunrise and sunset because —
A) Blue light is scattered most
B) Red light is scattered least
C) The atmosphere absorbs red light
D) None of the above
Answer: B) Red light is scattered least
Explanation: During sunrise and sunset, sunlight travels a longer path; blue light is scattered away, leaving red light visible.
97. The instrument used to measure the refractive index of liquids is —
A) Spectrometer
B) Microscope
C) Refractometer
D) Photometer
Answer: C) Refractometer
Explanation: A refractometer measures the degree to which light is bent (refracted) in a liquid.
98. The process by which the color of objects appears different in different lights is —
A) Dispersion
B) Selective absorption
C) Reflection
D) Diffraction
Answer: B) Selective absorption
Explanation: Objects absorb certain wavelengths and reflect others; thus, colors appear different under varied lighting.
99. The color of danger signals is red because —
A) It is most attractive
B) It scatters the least
C) It has the shortest wavelength
D) It travels the slowest
Answer: B) It scatters the least
Explanation: Red light, with the longest wavelength, can travel farther without scattering, making it ideal for warning signs.
100. The working of the human eye is similar to —
A) Microscope
B) Telescope
C) Camera
D) Prism
Answer: C) Camera
Explanation: The human eye functions like a camera — the lens focuses light on the retina (film), and the iris controls light entry (aperture).