Q.1 What is the speed of light in vacuum?
3 × 10^8 m/s
1.5 × 10^8 m/s
3 × 10^6 m/s
1 × 10^9 m/s
Explanation - Light travels at a constant speed of approximately 3 × 10^8 meters per second in vacuum.
Correct answer is: 3 × 10^8 m/s
Q.2 Which phenomenon explains why a straw looks bent in a glass of water?
Reflection
Refraction
Diffraction
Dispersion
Explanation - Refraction occurs when light bends as it passes from one medium to another with different optical density.
Correct answer is: Refraction
Q.3 What type of lens is used in a magnifying glass?
Concave lens
Convex lens
Bifocal lens
Cylindrical lens
Explanation - A convex lens converges light rays and magnifies objects, making it useful in magnifying glasses.
Correct answer is: Convex lens
Q.4 Which color of light has the shortest wavelength?
Red
Green
Violet
Yellow
Explanation - Violet light has the shortest wavelength (~400 nm) in the visible spectrum.
Correct answer is: Violet
Q.5 What happens when light hits a smooth and polished surface?
Diffuse reflection
Regular reflection
Absorption
Scattering
Explanation - A smooth surface reflects light uniformly, producing a clear image. This is regular reflection.
Correct answer is: Regular reflection
Q.6 Which optical instrument uses total internal reflection?
Microscope
Periscope
Kaleidoscope
Fiber optics
Explanation - Fiber optics technology uses total internal reflection to transmit light signals over long distances.
Correct answer is: Fiber optics
Q.7 The focal length of a convex lens is 10 cm. What is its power?
+10 D
+5 D
+20 D
+100 D
Explanation - Power (P) = 100 / f(cm). Here, P = 100 / 10 = +10 D.
Correct answer is: +10 D
Q.8 Which mirror is used as a rear-view mirror in vehicles?
Concave mirror
Convex mirror
Plane mirror
Parabolic mirror
Explanation - Convex mirrors provide a wider field of view, making them suitable as rear-view mirrors.
Correct answer is: Convex mirror
Q.9 What is the unit of the refractive index?
m/s
Joule
No unit
Candela
Explanation - Refractive index is the ratio of two speeds of light, hence it is dimensionless.
Correct answer is: No unit
Q.10 Which phenomenon forms a rainbow?
Reflection
Refraction and Dispersion
Diffraction
Polarization
Explanation - Raindrops refract and disperse sunlight into its constituent colors, forming a rainbow.
Correct answer is: Refraction and Dispersion
Q.11 What is the focal length of a plane mirror?
Zero
Infinity
One
Half
Explanation - A plane mirror has an infinite focal length as its radius of curvature is infinite.
Correct answer is: Infinity
Q.12 Which optical device is based on the principle of refraction through a prism?
Telescope
Spectrometer
Microscope
Camera
Explanation - A spectrometer uses prisms or diffraction gratings to separate and study light spectra.
Correct answer is: Spectrometer
Q.13 What type of image is formed by a concave mirror when the object is placed at the center of curvature?
Real, inverted, same size
Virtual, erect, magnified
Real, inverted, diminished
Virtual, erect, diminished
Explanation - At the center of curvature, the concave mirror forms a real, inverted image of the same size at the same point.
Correct answer is: Real, inverted, same size
Q.14 Which optical phenomenon makes the sky appear blue?
Reflection
Refraction
Dispersion
Scattering
Explanation - Rayleigh scattering of sunlight by air molecules makes the sky appear blue.
Correct answer is: Scattering
Q.15 Which lens is used to correct myopia (short-sightedness)?
Convex lens
Concave lens
Bifocal lens
Cylindrical lens
Explanation - A concave lens diverges light rays so that they can focus properly on the retina in myopic eyes.
Correct answer is: Concave lens
Q.16 What is the principle behind the working of a pinhole camera?
Rectilinear propagation of light
Refraction of light
Diffraction of light
Interference of light
Explanation - Light travels in straight lines, which helps in forming inverted images in a pinhole camera.
Correct answer is: Rectilinear propagation of light
Q.17 Which phenomenon causes the twinkling of stars?
Reflection
Refraction
Scattering
Diffraction
Explanation - Twinkling is caused by continuous refraction of starlight through atmospheric layers.
Correct answer is: Refraction
Q.18 Which optical effect is used in sunglasses to reduce glare?
Reflection
Dispersion
Polarization
Diffraction
Explanation - Polarized sunglasses reduce glare by blocking certain orientations of light waves.
Correct answer is: Polarization
Q.19 What type of mirror is used in torches?
Concave mirror
Convex mirror
Plane mirror
Parabolic mirror
Explanation - Concave mirrors focus light rays into a beam, which makes them useful in torches and headlights.
Correct answer is: Concave mirror
Q.20 Which law states that the angle of incidence equals the angle of reflection?
Snell’s law
Newton’s law
Law of Reflection
Law of Refraction
Explanation - According to the law of reflection, the angle of incidence is always equal to the angle of reflection.
Correct answer is: Law of Reflection
Q.21 Which type of wave is light?
Longitudinal wave
Transverse wave
Mechanical wave
Stationary wave
Explanation - Light is an electromagnetic transverse wave where oscillations are perpendicular to the direction of propagation.
Correct answer is: Transverse wave
Q.22 Which optical device is used in correcting astigmatism?
Convex lens
Concave lens
Cylindrical lens
Prism
Explanation - Cylindrical lenses correct astigmatism by compensating for uneven curvature of the cornea.
Correct answer is: Cylindrical lens
Q.23 In which part of the human eye does refraction mainly occur?
Lens
Cornea
Retina
Iris
Explanation - The cornea provides the largest refraction of light entering the eye.
Correct answer is: Cornea
Q.24 What happens when white light passes through a prism?
It remains white
It splits into seven colors
It disappears
It bends without color change
Explanation - Prisms disperse white light into its spectrum of seven colors due to varying refractive indices.
Correct answer is: It splits into seven colors
Q.25 Which optical principle is used in microscopes?
Reflection
Refraction
Diffraction
Polarization
Explanation - Microscopes use multiple convex lenses to bend and magnify light via refraction.
Correct answer is: Refraction