One of the most important topics in TNPSC Exam is “Light” from Physics because it explains how we see objects and how images are formed. Questions from Reflection and Refraction frequently asked in TNPSC General Science sections, covering mirrors, lenses, image formation, and the laws of light. Practice this quiz to strengthen your concepts with exam-oriented multiple-choice questions and detailed explanations.
TNPSC Physics Light Quiz 1 – Detailed Explanations
Understanding Reflection and Refraction is essential for scoring well in TNPSC Physics “Light”. Reflection occurs when light bounces back from a surface, while refraction is the bending of light as it passes from one medium to another due to a change in speed. These principles are applied in mirrors, lenses, optical instruments, cameras, microscopes, telescopes, spectacles, and even rainbows. Mastering these concepts helps you answer both direct and application-based questions confidently in TNPSC General Science examinations. The Detailed Explanations for Each Questions of this Quiz as follows
1. Light travels in the form of:
In geometrical optics, light is represented as rays, which are imaginary straight lines indicating the direction in which light travels. This representation helps explain important phenomena such as reflection, refraction, and image formation by mirrors and lenses. In a homogeneous medium, light travels in a straight line, a property known as rectilinear propagation of light.
🔹 Key Points
- A ray represents the direction of light travel.
- Light travels in straight lines through a homogeneous medium.
- Ray diagrams are used to study reflection and refraction.
- Geometrical optics is based on the concept of light rays.
🔹 Real-Life Example : The formation of sharp shadows and the beam from a torch demonstrate that light travels in straight lines.
✅ Answer: B. Rays
2. The bouncing back of light from a surface is called:
Reflection is the phenomenon in which light returns to the same medium after striking a surface. According to NCERT, reflection obeys two laws: the angle of incidence equals the angle of reflection, and the incident ray, reflected ray, and the normal lie in the same plane. Mirrors form images by reflecting light.
🔹 Key Points
- Reflection is the bouncing back of light.
- Occurs when light strikes a reflecting surface.
- Follows the laws of reflection.
- Used in mirrors and optical instruments.
🔹 Real-Life Example: Your image in a mirror is formed due to reflection of light.
✅ Answer: B. Reflection
3. The angle between the incident ray and the normal is called:
The angle of incidence is the angle between the incoming light ray and the normal drawn perpendicular to the reflecting surface at the point of incidence. It plays an important role in determining the direction of the reflected or refracted ray. This angle is always measured from the normal, not from the surface.
🔹 Key Points
- Measured between the incident ray and the normal.
- Represented by ∠i.
- Used in reflection and refraction.
- Always measured from the normal.
🔹 Real-Life Example : In school laboratory experiments, the angle of incidence is measured using a protractor.
✅ Answer: C. Angle of incidence
4. According to the law of reflection:
The first law of reflection states that the angle of incidence is always equal to the angle of reflection. This law is valid for all reflecting surfaces, including plane, concave and convex mirrors. It helps explain the formation of images by mirrors.
🔹 Key Points
- Angle of incidence = Angle of reflection.
- Measured from the normal.
- Applicable to all mirrors.
- Fundamental law of optics.
🔹 Real-Life Example : A torchlight reflected from a mirror follows this law.
✅ Answer: A. Angle of incidence = Angle of reflection
5. The mirror used as a rear-view mirror in vehicles is:
A convex mirror is used as a rear-view mirror because it provides a wider field of view than other mirrors. It always forms a virtual, erect and diminished image, allowing drivers to observe more of the road behind the vehicle.
🔹 Key Points
- Provides a wide field of view.
- Forms virtual and erect images.
- Images are diminished.
- Improves road safety.
🔹 Real-Life Example : Cars, buses and motorcycles use convex mirrors as rear-view mirrors.
✅ Answer: B. Convex mirror
6. A plane mirror forms an image that is:
A plane mirror always forms a virtual, erect and same-sized image. The image cannot be obtained on a screen because the reflected rays only appear to meet behind the mirror. The image is laterally inverted and is formed at the same distance behind the mirror as the object is in front.
🔹 Key Points
- Image is virtual and erect.
- Same size as the object.
- Laterally inverted.
- Equal object and image distance.
🔹 Real-Life Example : Looking into a dressing mirror produces a virtual and erect image.
✅ Answer: B. Virtual and erect
7. The bending of light when it passes from one medium to another is called:
Refraction is the bending of light when it travels from one transparent medium to another due to a change in its speed. Light bends towards the normal when entering a denser medium and away from the normal when entering a rarer medium.
🔹 Key Points
- Caused by change in speed of light.
- Occurs between two transparent media.
- Light bends towards the normal in a denser medium.
- Forms the basis of lenses.
🔹 Real-Life Example : A pencil appears bent when partially immersed in water.
✅ Answer: B. Refraction
8. Which medium has the highest speed of light?
Light travels fastest in a vacuum because there are no particles to slow its motion. When light enters air, water or glass, its speed decreases depending on the optical density of the medium.
🔹 Key Points
- Maximum speed in vacuum.
- Speed decreases in material media.
- Approximate speed is 3 × 10⁸ m/s.
- Speed depends on the medium.
🔹 Real-Life Example : Sunlight travels through space, which is nearly a vacuum.
✅ Answer: D. Vacuum
9. The splitting of white light into different colors is called:
Dispersion is the splitting of white light into its constituent colours when it passes through a prism. Different colours bend by different amounts because each colour has a different wavelength.
🔹 Key Points
- Produces seven colours.
- Caused by different refractions.
- Demonstrated using a prism.
- Forms a visible spectrum.
🔹 Real-Life Example : A glass prism separates sunlight into VIBGYOR colours.
✅ Answer: C. Dispersion
10. The seven colors of visible light together form:
The seven colours Violet, Indigo, Blue, Green, Yellow, Orange and Red (VIBGYOR) together form the visible spectrum. These colours are produced when white light undergoes dispersion.
🔹 Key Points
- Contains seven visible colours.
- Produced by dispersion.
- Called the visible spectrum.
- White light contains all seven colours.
🔹 Real-Life Example : The colors seen in a rainbow form the visible spectrum.
✅ Answer: B. Spectrum
11. Which color has the longest wavelength?
Among the visible colours, red light has the longest wavelength. Due to its longer wavelength, it bends the least during refraction and is visible from a greater distance.
🔹 Key Points
- Longest wavelength.
- Least deviation.
- Lower frequency.
- Visible over longer distances.
🔹 Real-Life Example : Traffic stop signals use red light because it can be seen from farther away.
✅ Answer: D. Red
12. Which color has the shortest wavelength?
Violet light has the shortest wavelength in the visible spectrum. It undergoes the maximum deviation while passing through a prism because of its shorter wavelength.
🔹 Key Points
- Shortest wavelength.
- Maximum deviation.
- Highest frequency.
- Appears at one end of the spectrum.
🔹 Real-Life Example : Violet light bends more than red light in a glass prism.
✅ Answer: C. Violet
13. The device used to observe dispersion of light is:
A glass prism is used to demonstrate the dispersion of white light. It refracts each colour by a different amount, producing the visible spectrum.
🔹 Key Points
- Separates white light.
- Produces VIBGYOR.
- Works by refraction.
- Common optical device.
🔹 Real-Life Example : Science laboratories use prisms to demonstrate dispersion.
✅ Answer: B. Prism
14. The image formed by a concave mirror can be:
A concave mirror can produce either a real or a virtual image, depending on the position of the object. If the object is placed beyond the focus, a real image is formed. If it is placed between the focus and the mirror, a virtual image is formed.
🔹 Key Points
- Forms real or virtual images.
- Depends on object position.
- Real images can be projected.
- Virtual images cannot be projected.
🔹 Real-Life Example : Dentists use concave mirrors to obtain enlarged virtual images.
✅ Answer: C. Both real and virtual
15. The mirror used in shaving mirrors is:
A concave mirror is used as a shaving mirror because it forms a magnified, erect virtual image when the face is placed close to the mirror. This helps in viewing fine details clearly.
🔹 Key Points
- Produces magnified images.
- Image is erect and virtual.
- Used for close observation.
- Also used by dentists.
🔹 Real-Life Example : Barbers commonly use concave mirrors while shaving.
✅ Answer: C. Concave mirror
16. A rainbow is formed due to:
A rainbow is formed when sunlight enters water droplets, undergoes refraction, internal reflection and dispersion, and finally emerges as seven colours. Millions of droplets together produce the colourful arc seen in the sky.
🔹 Key Points
- Involves refraction.
- Includes internal reflection.
- Produces dispersion.
- Forms VIBGYOR colours.
🔹 Real-Life Example : Rainbows are commonly seen after rainfall when sunlight shines.
✅ Answer: B. Refraction and dispersion
17. The image distance in a plane mirror is:
In a plane mirror, the image is formed at the same distance behind the mirror as the object is in front of it. This is one of the important characteristics of images formed by plane mirrors.
🔹 Key Points
- Image distance equals object distance.
- Image is virtual.
- Image is erect.
- Image is same size.
🔹 Real-Life Example : Moving closer to a mirror makes the image move closer by the same distance.
✅ Answer: A. Equal to object distance
18. Light travels in straight lines. This property is called:
The property by which light travels in straight lines through a homogeneous transparent medium is called rectilinear propagation of light. This principle explains the formation of shadows and eclipses.
🔹 Key Points
- Light travels in straight lines.
- Valid in homogeneous media.
- Explains shadow formation.
- Basis of ray diagrams.
🔹 Real-Life Example : The shadow of a tree on a sunny day demonstrates rectilinear propagation.
✅ Answer: A. Rectilinear propagation
19. The speed of light in vacuum is approximately:
The speed of light in a vacuum is approximately 3 × 10⁸ metres per second, the highest speed possible in nature. This value decreases when light travels through other transparent media.
🔹 Key Points
- Approximately 3 × 10⁸ m/s.
- Highest speed in nature.
- Maximum in vacuum.
- Decreases in glass and water.
🔹 Real-Life Example : Light from the Sun reaches Earth in about 8 minutes 20 seconds.
✅ Answer: B. 3 × 10⁸ m/s
20. The phenomenon responsible for the twinkling of stars is:
Stars appear to twinkle due to atmospheric refraction. As starlight passes through layers of the Earth’s atmosphere with varying densities, it is continuously refracted, causing the apparent brightness and position of stars to change.
🔹 Key Points
- Caused by atmospheric refraction.
- Atmosphere has varying densities.
- Stars appear to change brightness.
- Planets usually do not twinkle noticeably.
🔹 Real-Life Example : Stars sparkle in the night sky, especially near the horizon.
✅ Answer: C. Atmospheric refraction
Final Revision Tips
- Light travels in straight lines.
- Reflection follows the law: angle of incidence = angle of reflection.
- Refraction occurs when light moves from one medium to another.
- A plane mirror forms a virtual and erect image.
- Convex mirrors are used as rear-view mirrors in vehicles.
- Dispersion splits white light into seven colors (VIBGYOR).
- Red light has the longest wavelength, while violet has the shortest.
- A rainbow forms due to dispersion, refraction and reflection of light.
- The speed of light in vacuum is 3 × 10⁸ m/s.
- Twinkling of stars occurs due to atmospheric refraction.
Further Reading
To strengthen your understanding of Reflection and Refraction, study the official NCERT chapter covering the laws of reflection, refraction, spherical mirrors, lenses, image formation, and numerical applications. This chapter builds the fundamental concepts frequently tested in TNPSC Physics Light and other competitive examinations.
Authority: NCERT – Class 10 Science, Chapter 10: Light – Reflection and Refraction
