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Light & Optics — Homi Bhabha Exam Physics MCQs with Solutions
Free Homi Bhabha Exam Physics Light & Optics MCQs with step-by-step solutions covering Reflection & Refraction, Spherical Mirrors, Lenses, Shadow Formation, Dispersion through a Prism, Optical Instruments. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Reflection & Refraction · hard · numerical
A ray of light strikes a plane mirror making an angle of 30° with the mirror surface. The angle of reflection (measured from the normal) is:
A. 120°
B. 30°
C. 90°
D. 60° ✓ Correct
Solution: The angle of incidence from the normal $= 90° - 30° = 60°$, so the angle of reflection is also 60°.
Q2 — Reflection & Refraction · hard · theory
The speed of light is greatest in:
A. diamond
B. vacuum ✓ Correct
C. glass
D. water
Solution: Light travels fastest in vacuum; denser media (water, glass, diamond) slow it down.
Q3 — Spherical Mirrors · hard · numerical
A concave mirror has a focal length of 15 cm. Its radius of curvature is:
A. 7.5 cm
B. 30 cm ✓ Correct
C. 45 cm
D. 15 cm
Solution: Radius of curvature $R = 2f = 2 \times 15 = 30$ cm.
Q4 — Spherical Mirrors · hard · theory
When an object is placed beyond the centre of curvature of a concave mirror, the image formed is:
A. real, inverted and diminished ✓ Correct
B. virtual and diminished
C. real, erect and magnified
D. virtual, erect and magnified
Solution: For an object beyond C, a concave mirror forms a real, inverted, diminished image between F and C.
Q5 — Lenses · hard · numerical
The power of a lens of focal length 25 cm is:
A. +4 D ✓ Correct
B. +2.5 D
C. +0.25 D
D. +25 D
Solution: $f = 25$ cm $= 0.25$ m, so power $= \dfrac{1}{0.25} = +4$ D.
Q6 — Lenses · hard · theory
A concave lens always forms an image that is:
A. real, inverted and magnified
B. virtual, erect and diminished ✓ Correct
C. real and erect
D. virtual and magnified
Solution: For all object positions, a concave (diverging) lens forms a virtual, erect, diminished image.
Q7 — Shadow Formation · hard · theory
The dark central region of a shadow, where light is completely blocked, is called the:
A. umbra ✓ Correct
B. focus
C. aperture
D. penumbra
Solution: The umbra is the fully dark part; the lighter surrounding region is the penumbra.
Q8 — Shadow Formation · hard · theory
A shadow is formed only by an object that is:
A. opaque ✓ Correct
B. translucent
C. transparent
D. luminous
Solution: Opaque objects block light and cast shadows; transparent objects let light pass through.
Q9 — Dispersion through a Prism · hard · theory
When white light is dispersed by a prism, the colour that bends the least is:
A. blue
B. violet
C. green
D. red ✓ Correct
Solution: Red light has the longest wavelength and is deviated least; violet is deviated most.
Q10 — Dispersion through a Prism · hard · theory
Different colours of light are dispersed by a prism because in glass they travel at:
A. infinite speed
B. different speeds and so bend by different amounts ✓ Correct
C. the speed of sound
D. the same speed
Solution: Each colour has a slightly different speed (and refractive index) in glass, so each bends by a different amount.
Q11 — Optical Instruments · hard · theory
A periscope, used in submarines to see above the water, works using:
A. a concave mirror only
B. two plane mirrors (or prisms) inclined at 45° ✓ Correct
C. a prism that disperses light
D. a single convex lens
Solution: Two parallel mirrors at 45° reflect light down the tube, letting the viewer see over obstacles.
Q12 — Optical Instruments · hard · theory
The image formed on the film/sensor of a camera is:
A. virtual and diminished
B. real, erect and magnified
C. virtual, erect and magnified
D. real, inverted and diminished ✓ Correct
Solution: A camera's convex lens forms a real, inverted, diminished image of a distant object on the film/sensor.
Q13 — Reflection & Refraction · medium · theory
According to the laws of reflection, the angle of incidence is:
A. less than the angle of reflection
B. greater than the angle of reflection
C. equal to the angle of reflection ✓ Correct
D. always 90°
Solution: The angle of incidence equals the angle of reflection, both measured from the normal.
Q14 — Reflection & Refraction · medium · theory
When light travels from air into a denser medium such as glass, it bends:
A. away from the normal
B. along the surface
C. back into air
D. towards the normal ✓ Correct
Solution: On entering a denser medium light slows down and bends towards the normal (refraction).
Q15 — Reflection & Refraction · medium · theory
A pencil placed in a glass of water appears bent at the water surface because of:
A. dispersion of light
B. absorption of light
C. refraction of light ✓ Correct
D. reflection of light
Solution: Light from the submerged part bends as it leaves the water, making the pencil appear bent.
Q16 — Spherical Mirrors · medium · theory
A concave mirror is used as a shaving/make-up mirror because, when the face is close to it, it forms an image that is:
A. real and inverted
B. erect and magnified ✓ Correct
C. inverted and diminished
D. the same size
Solution: For an object within its focus, a concave mirror gives an erect, magnified (virtual) image.
Q17 — Spherical Mirrors · medium · theory
A convex mirror is preferred as a rear-view mirror in vehicles because it:
A. gives an inverted image
B. shows a narrow field of view
C. gives a magnified image
D. gives an erect, diminished image and a wider field of view ✓ Correct
Solution: A convex mirror always forms an erect, smaller image and covers a wider area behind the vehicle.
Q18 — Spherical Mirrors · medium · numerical
The focal length of a spherical mirror of radius of curvature 20 cm is:
A. 5 cm
B. 40 cm
C. 10 cm ✓ Correct
D. 20 cm
Solution: Focal length $= \dfrac{R}{2} = \dfrac{20}{2} = 10$ cm.
Q19 — Lenses · medium · theory
A convex lens is also called a converging lens because it:
A. spreads parallel rays apart
B. absorbs light
C. brings parallel rays of light together at a focus ✓ Correct
D. reflects light
Solution: A convex lens converges parallel rays to a real focus, unlike a concave (diverging) lens.
Q20 — Lenses · medium · theory
A magnifying glass (simple microscope) uses a:
A. plane mirror
B. convex lens ✓ Correct
C. convex mirror
D. concave lens
Solution: A convex lens held close to an object gives an enlarged, erect, virtual image — a magnifying glass.
Q21 — Lenses · medium · numerical
The power of a convex lens of focal length 0.5 m is:
A. −2 D
B. +2 D ✓ Correct
C. +0.5 D
D. +5 D
Solution: Power $= \dfrac{1}{f(\text{m})} = \dfrac{1}{0.5} = +2$ dioptre (positive for a convex lens).
Q22 — Shadow Formation · medium · theory
Shadows are formed because light travels:
A. around obstacles
B. in curved paths
C. in straight lines (rectilinear propagation) ✓ Correct
D. faster through opaque objects
Solution: Since light travels in straight lines, an opaque object blocks it and casts a shadow.
Q23 — Shadow Formation · medium · theory
A solar eclipse occurs when:
A. the Sun comes between the Earth and the Moon
B. the Moon comes between the Sun and the Earth ✓ Correct
C. the Earth stops rotating
D. the Earth comes between the Sun and the Moon
Solution: In a solar eclipse the Moon's shadow falls on the Earth, blocking the Sun.
Q24 — Shadow Formation · medium · theory
A lunar eclipse occurs when:
A. the Moon comes between the Sun and the Earth
B. the Sun is blocked by a planet
C. the Earth comes between the Sun and the Moon ✓ Correct
D. the Moon enters the Sun
Solution: In a lunar eclipse the Earth's shadow falls on the Moon.
Q25 — Dispersion through a Prism · medium · theory
When white light passes through a glass prism, it splits into seven colours. This phenomenon is called:
A. refraction only
B. dispersion ✓ Correct
C. diffraction
D. reflection
Solution: Dispersion is the splitting of white light into its constituent colours (VIBGYOR).
Q26 — Dispersion through a Prism · medium · theory
A rainbow is formed by the dispersion of sunlight by:
A. the ozone layer
B. dust particles
C. tiny water droplets in the atmosphere ✓ Correct
D. clouds reflecting light
Solution: Water droplets act like tiny prisms, dispersing sunlight into a rainbow.
Q27 — Dispersion through a Prism · medium · theory
The correct order of colours in the visible spectrum (VIBGYOR) from the least deviated to the most deviated is:
A. Red, Orange, Yellow, Green, Blue, Indigo, Violet ✓ Correct
B. Violet, Indigo, Blue, Green, Yellow, Orange, Red
C. Blue, Green, Red, Yellow, Violet, Orange, Indigo
D. Red, Yellow, Orange, Blue, Green, Violet, Indigo
Solution: Red bends least and violet most, so from least to most deviated: R, O, Y, G, B, I, V.
Q28 — Optical Instruments · medium · theory
A simple microscope (magnifying glass) is essentially a:
A. single convex lens of short focal length ✓ Correct
B. convex mirror
C. plane mirror
D. concave lens
Solution: A simple microscope is a short-focal-length convex lens that gives an enlarged virtual image.
Q29 — Optical Instruments · medium · theory
A telescope is an optical instrument used to view:
A. distant objects such as stars and planets ✓ Correct
B. very small nearby objects
C. objects inside the body
D. objects in the dark
Solution: A telescope magnifies far-off objects like celestial bodies.
Q30 — Optical Instruments · medium · theory
The lens present in the human eye is a:
A. concave lens
B. convex mirror
C. plane glass
D. convex lens ✓ Correct
Solution: The eye lens is convex; it focuses light onto the retina to form a real, inverted image.