Q.1 The speed of light is maximum in which of the following mediums?
Water
Glass
Air
Diamond
Explanation - The speed of light is highest in vacuum or air since the refractive index is lowest, leading to minimal interaction with the medium.
Correct answer is: Air
Q.2 The unit of focal length is:
Diopter
Meter
Centimeter
Candela
Explanation - Focal length is measured in units of length, typically meters, centimeters, etc. Diopter is the unit of power, not focal length.
Correct answer is: Meter
Q.3 Which of the following optical phenomena is responsible for the twinkling of stars?
Reflection
Refraction
Dispersion
Diffraction
Explanation - Twinkling occurs due to atmospheric refraction where light bends irregularly due to varying air densities.
Correct answer is: Refraction
Q.4 If the angle of incidence equals the angle of reflection, this is a case of:
Refraction
Reflection
Diffraction
Interference
Explanation - According to the law of reflection, the angle of incidence equals the angle of reflection.
Correct answer is: Reflection
Q.5 The refractive index of water is 1.33. The speed of light in water is approximately:
2.25 × 10^8 m/s
3.00 × 10^8 m/s
2.00 × 10^8 m/s
1.50 × 10^8 m/s
Explanation - Speed of light v = c/n = (3.00 × 10^8) / 1.33 ≈ 2.25 × 10^8 m/s.
Correct answer is: 2.25 × 10^8 m/s
Q.6 A concave mirror forms a virtual, erect, and magnified image when the object is placed:
Beyond the center of curvature
Between focus and pole
At infinity
At the center of curvature
Explanation - For a concave mirror, a virtual and magnified image is formed when the object is between the pole and the focus.
Correct answer is: Between focus and pole
Q.7 The power of a convex lens of focal length 50 cm is:
+2 D
-2 D
+0.5 D
-0.5 D
Explanation - Power P = 100 / focal length in cm = 100 / 50 = +2 D for a convex lens.
Correct answer is: +2 D
Q.8 A plane mirror produces an image that is:
Real, erect, same size
Virtual, erect, same size
Virtual, inverted, same size
Real, inverted, magnified
Explanation - Plane mirrors always form virtual, erect images of the same size as the object.
Correct answer is: Virtual, erect, same size
Q.9 The phenomenon of rainbow formation is due to:
Reflection
Refraction and Dispersion
Diffraction
Interference
Explanation - Rainbows occur because sunlight refracts and disperses into its constituent colors in water droplets.
Correct answer is: Refraction and Dispersion
Q.10 For a convex lens, if the object is at 2F, the image will be:
Virtual, erect, same size
Real, inverted, same size
Real, erect, magnified
Virtual, inverted, magnified
Explanation - When the object is at 2F for a convex lens, the image forms at 2F and is real, inverted, and same size.
Correct answer is: Real, inverted, same size
Q.11 The human eye lens is a:
Concave lens
Convex lens
Plane mirror
Concave mirror
Explanation - The eye lens is a convex lens that converges light rays onto the retina.
Correct answer is: Convex lens
Q.12 Critical angle is the angle of incidence for which:
Angle of refraction is 0°
Angle of refraction is 90°
Angle of incidence is 90°
Total internal reflection does not occur
Explanation - At the critical angle, the refracted ray travels along the boundary, making 90° with the normal.
Correct answer is: Angle of refraction is 90°
Q.13 The focal length of a concave mirror is 20 cm. Its radius of curvature is:
10 cm
20 cm
30 cm
40 cm
Explanation - Radius of curvature R = 2 × focal length = 40 cm.
Correct answer is: 40 cm
Q.14 A prism works on the principle of:
Reflection
Refraction
Diffraction
Scattering
Explanation - A prism bends light due to refraction at its two surfaces.
Correct answer is: Refraction
Q.15 The color of the sky appears blue because of:
Reflection
Scattering of light
Refraction
Dispersion
Explanation - Shorter wavelengths like blue are scattered more by air molecules, making the sky appear blue.
Correct answer is: Scattering of light
Q.16 The magnifying power of a simple microscope depends on:
Size of lens
Focal length of lens
Refractive index of medium
Curvature of mirror
Explanation - Magnifying power is inversely proportional to the focal length of the lens used.
Correct answer is: Focal length of lens
Q.17 The principle of the periscope is based on:
Refraction
Total internal reflection
Diffraction
Scattering
Explanation - Periscopes use total internal reflection inside prisms to redirect light.
Correct answer is: Total internal reflection
Q.18 An object placed in front of a convex mirror will always have an image that is:
Virtual and diminished
Real and diminished
Virtual and magnified
Real and magnified
Explanation - A convex mirror always forms virtual, erect, and diminished images regardless of object position.
Correct answer is: Virtual and diminished
Q.19 The phenomenon of mirage occurs due to:
Reflection
Total internal reflection
Diffraction
Interference
Explanation - Mirages form due to total internal reflection of light in layers of air with varying densities.
Correct answer is: Total internal reflection
Q.20 Which optical instrument uses both a concave and a convex lens?
Camera
Simple microscope
Telescope
Compound microscope
Explanation - A compound microscope uses a combination of lenses: a convex objective and a concave or convex eyepiece.
Correct answer is: Compound microscope
Q.21 The refractive index of diamond is about:
1.33
1.5
2.42
2.0
Explanation - Diamond has a very high refractive index, approximately 2.42, leading to strong brilliance.
Correct answer is: 2.42
Q.22 The lens used in a magnifying glass is:
Concave lens
Convex lens
Bifocal lens
Cylindrical lens
Explanation - Convex lenses are used to magnify objects as they converge light rays.
Correct answer is: Convex lens
Q.23 Dispersion of light occurs because:
All colors have the same speed in a medium
Different colors travel at different speeds in a medium
Reflection at different angles
Interference of light
Explanation - Dispersion occurs because different wavelengths of light refract by different amounts.
Correct answer is: Different colors travel at different speeds in a medium
Q.24 In a camera, the lens forms:
Virtual, erect, diminished image
Real, inverted, diminished image
Virtual, inverted, magnified image
Real, erect, same size image
Explanation - Camera lenses form real, inverted, and generally diminished images on the film or sensor.
Correct answer is: Real, inverted, diminished image
Q.25 The phenomenon used in optical fibers is:
Reflection
Refraction
Total internal reflection
Dispersion
Explanation - Light in optical fibers is guided by total internal reflection within the fiber core.
Correct answer is: Total internal reflection