Light TNPSC Questions help you revise important Physics concepts through exam-oriented multiple-choice questions. Attempt this TNPSC Physics Light Quiz to test your knowledge and improve your General Science preparation. Practice these TNPSC Physics MCQs to improve your accuracy, build confidence, and enhance your preparation with detailed answers and explanations. Whether you are revising or testing your knowledge, these TNPSC Science Questions will help you perform better in the exam.
Light TNPSC Questions – Detailed Explanations
Practice these Light TNPSC Questions with detailed answers and easy-to-understand explanations. This section helps you revise important concepts on reflection, refraction, lenses, mirrors, and the human eye, making it ideal for TNPSC Physics Light Quiz preparation and other competitive exams.
1. Which property of light enables us to see objects that do not produce their own light?
Answer: Reflection
Explanation:
Most objects around us, such as books, trees, tables, and buildings, do not emit their own light. They become visible because light from a source like the Sun or an electric bulb falls on them and reflects into our eyes. This reflected light allows the brain to recognize the object. Without reflection, non-luminous objects would remain invisible.
Quick Revision:
- Luminous objects produce their own light.
- Non-luminous objects are seen due to reflected light.
- Reflection follows the laws of reflection.
Real-Life Example:
A chair inside a room is visible because it reflects light from the room’s bulb.
2. Which phenomenon explains the apparent bending of a stick partially immersed in water?
Answer: Refraction
Explanation:
Refraction is the bending of light when it passes from one transparent medium to another with different optical densities, such as water to air. Since light changes speed while crossing the boundary, the submerged portion of the stick appears bent even though it is actually straight.
Quick Revision:
- Refraction occurs due to a change in the speed of light.
- Light bends at the boundary between two media.
- Optical density determines the amount of bending.
Real-Life Example:
A spoon placed in a glass of water appears bent because of refraction.
3. A convex mirror is preferred as a rear-view mirror mainly because it:
Answer: Provides a wider field of view
Explanation:
A convex mirror diverges reflected light and forms a virtual, erect, and diminished image. This enables the driver to view a much larger area behind the vehicle, reducing blind spots and improving road safety.
Quick Revision:
- Convex mirror → virtual, erect, diminished image.
- Gives a wider field of view.
- Used in vehicles for safety.
Real-Life Example:
Rear-view mirrors on cars, buses, and motorcycles are convex mirrors.
4. Which mirror should be used to obtain a real image on a screen?
Answer: Concave Mirror
Explanation:
A concave mirror converges parallel rays of light. When an object is placed beyond the focal point, it forms a real image that can be projected onto a screen. Plane and convex mirrors always produce virtual images that cannot be captured on a screen.
Quick Revision:
- Only a concave mirror forms real images.
- Real images can be projected on a screen.
- Position of the object determines image characteristics.
Real-Life Example:
A concave mirror is used in reflecting telescopes to focus light.
5. Which lens is used in a simple magnifier?
Answer: Convex Lens
Explanation:
A simple magnifier uses a convex lens to produce an enlarged, virtual, and erect image when the object is placed within its focal length. This helps in observing fine details that are difficult to see with the naked eye.
Quick Revision:
- Convex lens acts as a magnifying glass.
- Produces a virtual and enlarged image.
- Object should be within the focal length.
Real-Life Example:
Jewellers use convex lenses to inspect precious stones.
6. A person cannot see nearby objects clearly but can see distant objects. The defect is:
Answer: Hypermetropia
Explanation:
Hypermetropia, or long-sightedness, occurs when the image of a nearby object forms behind the retina due to insufficient converging power of the eye lens or a shorter eyeball. It is corrected using a convex lens.
Quick Revision:
- Hypermetropia = difficulty seeing near objects.
- Image forms behind the retina.
- Corrected using a convex lens.
Real-Life Example:
People with hypermetropia use reading glasses while reading books.
7. The image formed on the retina is:
Answer: Real and Inverted
Explanation:
The eye lens focuses incoming light onto the retina and forms a real, inverted, and smaller image. The brain processes this information and interprets the object in its correct upright position.
Quick Revision:
- Retina receives a real and inverted image.
- Brain interprets the image correctly.
- Eye lens functions like a convex lens.
Real-Life Example:
Every object you see forms an inverted image on your retina before being processed by the brain.
8. Which optical phenomenon causes stars to twinkle?
Answer: Atmospheric Refraction
Explanation:
Starlight passes through several layers of the Earth’s atmosphere, each having different densities. Continuous bending of light due to changing air density causes the apparent brightness and position of stars to fluctuate, producing the twinkling effect.
Quick Revision:
- Twinkling occurs due to atmospheric refraction.
- Air density continuously changes.
- Planets generally do not twinkle noticeably.
Real-Life Example:
Stars appear to sparkle more on clear winter nights.
9. Which colour deviates the least while passing through a glass prism?
Answer: Red
Explanation:
Red light has the longest wavelength among visible colours and experiences the smallest change in speed inside a prism. Therefore, it bends the least compared to other colours.
Quick Revision:
- Red → least deviation.
- Violet → maximum deviation.
- Deviation depends on wavelength.
Real-Life Example:
Red appears at the top of a rainbow because it bends less.
10. The splitting of white light into seven colours demonstrates:
Answer: Dispersion
Explanation:
Dispersion occurs because different colours of light have different wavelengths and refractive indices in glass. As white light passes through a prism, each colour bends by a different amount, producing the visible spectrum.
Quick Revision:
- Dispersion separates white light.
- Prism produces VIBGYOR.
- Different wavelengths bend differently.
Real-Life Example:
A crystal prism placed in sunlight produces rainbow colours.
11. Which optical device uses two convex lenses?
Answer: Compound Microscope
Explanation:
A compound microscope contains two convex lenses: the objective lens forms a magnified real image, while the eyepiece further magnifies it to produce a large virtual image for detailed observation.
Quick Revision:
- Two convex lenses.
- Objective + Eyepiece.
- Used to observe tiny objects.
Real-Life Example:
Biologists use compound microscopes to study cells and microorganisms.
12. The principal function of the iris is to:
Answer: Control the amount of light entering the eye
Explanation:
The iris is the coloured part of the eye. It adjusts the size of the pupil according to the intensity of light, allowing more light in dim conditions and less light in bright conditions to protect the retina.
Quick Revision:
- Iris controls pupil size.
- Regulates light entering the eye.
- Protects the retina.
Real-Life Example:
Your pupils become smaller when you step into bright sunlight.
13. The refractive index of a medium depends mainly on:
Answer: Speed of Light in the Medium
Explanation:
The refractive index measures how much light slows down in a medium compared to its speed in a vacuum. A higher refractive index means light travels more slowly and bends more strongly.
Quick Revision:
- Refractive index depends on light speed.
- Greater refractive index → more bending.
- Symbol: n = c/v.
Real-Life Example:
Light bends more in glass than in air because it travels slower in glass.
14. Which mirror is commonly used in vehicle headlamps?
Answer: Concave Mirror
Explanation:
A concave mirror reflects light from the bulb placed at its focus into a strong, nearly parallel beam. This increases the illumination distance, making night driving safer.
Quick Revision:
- Concave mirror produces parallel beams.
- Used in headlights and torches.
- Improves illumination.
Real-Life Example:
Car headlights use concave mirrors to project light far ahead.
15. Which part of the eye contains light-sensitive cells?
Answer: Retina
Explanation:
The retina contains rods and cones, which are specialized cells that detect light. Rods help us see in dim light, while cones enable colour vision and sharp vision in bright light.
Quick Revision:
- Retina contains rods and cones.
- Rods → night vision.
- Cones → colour vision.
Real-Life Example:
The retina functions like the image sensor in a digital camera.
16. The normal drawn at the point of incidence is always:
Answer: Perpendicular to the Reflecting Surface
Explanation:
The normal is an imaginary line drawn at right angles (90°) to the reflecting surface at the point where the incident ray strikes. Angles of incidence and reflection are measured with respect to this normal.
Quick Revision:
- Normal is perpendicular to the surface.
- Used to measure angles.
- Essential in reflection and refraction.
Real-Life Example:
Ray diagrams in optics always begin by drawing the normal.
17. The colour of the clear daytime sky is mainly due to:
Answer: Scattering of Light
Explanation:
Air molecules scatter shorter wavelengths of sunlight, especially blue light, more effectively than longer wavelengths like red. As a result, blue light reaches our eyes from all directions, making the sky appear blue.
Quick Revision:
- Blue light scatters the most.
- Caused by atmospheric molecules.
- Known as Rayleigh scattering.
Real-Life Example:
The sky looks blue on a clear afternoon because of scattering.
18. Which phenomenon is responsible for the formation of a rainbow?
Answer: Refraction, Dispersion and Internal Reflection
Explanation:
When sunlight enters a raindrop, it first refracts and disperses into different colours. The light then undergoes internal reflection inside the drop and refracts again while leaving it, producing the colourful rainbow.
Quick Revision:
- Rainbow needs sunlight and raindrops.
- Three processes: refraction, dispersion, internal reflection.
- Forms opposite the Sun.
Real-Life Example:
A rainbow often appears after rain when sunlight shines through water droplets.
19. The eye defect corrected using a concave lens is:
Answer: Myopia
Explanation:
Myopia, or short-sightedness, occurs when distant objects appear blurred because their images form in front of the retina. A concave lens diverges incoming light so that the image forms correctly on the retina.
Quick Revision:
- Myopia = difficulty seeing distant objects.
- Image forms in front of the retina.
- Corrected using a concave lens.
Real-Life Example:
Students with myopia wear concave-lens spectacles to clearly see the classroom board.
20. Which statement about a plane mirror is correct?
Answer: It forms a virtual image of the same size.
Explanation:
A plane mirror forms an erect, virtual image that is equal in size to the object and appears at the same distance behind the mirror as the object is in front. Such an image cannot be projected onto a screen.
Quick Revision:
- Plane mirror forms a virtual image.
- Image is erect and same size.
- Image distance equals object distance.
Real-Life Example:
The mirror in a bathroom forms a virtual image of your face with the same size.
Further Reading:
A few minutes of textbook revision can make a big difference in competitive exams. The official NCERT chapter below explains the essential concepts covered in these TNPSC Science Questions.
Official NCERT Resource: Light – Reflection and Refraction
