Class 8 Science Chapter 10: Light – Mirrors and Lenses Solutions

1. Multiple choice questions.

1. A light ray is incident on a mirror and gets reflected by it (Fig. 10.21). The angle made by the incident ray with the normal to the mirror is 40°. What is the angle made by the reflected ray with the mirror?

• (i) 40°
• (ii) 50°
• (iii) 45°
• (iv) 60°

Answer: (ii) 50°

2. When the light is incident along the normal on the mirror, which is true:

• (i) Angle of incidence is 90°
• (ii) Angle of incidence is 0°
• (iii) Angle of reflection is 90°
• (iv) No reflection of light takes place in this case

Answer: (ii) Angle of incidence is 0°

3. Match the following.

4. Assertion/Reason Type:

Why are convex mirrors used for rear-view? Is it because of a larger view area?

Answer: Yes, convex mirrors are used for rear-view in vehicles because they provide a wider field of view, allowing drivers to see more area behind them even though the image appears smaller and erect.

2. Answer the following questions in about 30 words.

1. Why do side-view mirrors of vehicles carry the warning “Objects in mirror are closer than they appear”?

Answer: Side-view mirrors are convex mirrors. Convex mirrors always form diminished, erect images, so objects appear smaller and farther than they actually are. Thus, the warning is given to alert drivers that vehicles are actually closer than they seem in the mirror.

2. With the help of a diagram, distinguish between a concave and convex mirror.

Answer: A concave mirror has its reflecting surface curved inward, like a cave, and can form real or virtual images. A convex mirror has its reflecting surface curved outward and always forms virtual, erect, and diminished images. (Refer to textbook Fig. 10.2 and 10.3.)

3. What are the characteristics of images formed by concave and convex mirrors?

Answer: A concave mirror can form enlarged, diminished, or same size images, which may be erect or inverted depending on object distance. A convex mirror forms images that are always diminished, erect, and virtual.

4. Give one important use each of a concave and a convex mirror.

Answer: Concave mirrors are used by dentists to view enlarged images of teeth. Convex mirrors are used as rear-view (side-view) mirrors in vehicles as they provide a wider field of view.

5. State the laws of reflection.

Answer: The laws of reflection are: (1) The angle of incidence is equal to the angle of reflection. (2) The incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane.

6. What is a lens? Name its two types.

Answer: A lens is a transparent piece of glass or plastic with at least one curved surface. The two main types of lenses are convex (converging) lens and concave (diverging) lens.

7. What is the difference between a convex lens and a concave lens?

Answer: A convex lens is thicker in the middle and thinner at the edges and converges parallel light rays. A concave lens is thinner in the middle and thicker at the edges and diverges parallel light rays.

8. Give one application each of convex and concave lenses.

Answer: Convex lenses are used as magnifying glasses and in cameras. Concave lenses are used in spectacles to correct short-sightedness (myopia).

3. Answer the following questions in about 150 words.

1. Explain with the help of activities how image formation takes place in concave and convex mirrors with change in object distance.

Answer: Activity 10.3 demonstrates that when an object is placed close to a concave mirror, the image formed is erect and enlarged. As the object is moved farther from the mirror, the image becomes inverted and shrinks. In case of a convex mirror, the image remains erect and diminished regardless of the object's distance. Thus, concave mirrors can produce both real and virtual images depending on the position of the object, while convex mirrors always produce virtual, erect, and diminished images.

2. Describe the laws of reflection and explain how they can be verified experimentally.

Answer: The laws of reflection are: (1) The angle of incidence equals the angle of reflection; (2) The incident ray, the normal, and the reflected ray lie in the same plane. To verify, a narrow beam of light is passed onto a plane mirror at different angles (as in Activity 10.4). The angles of incidence and reflection are measured and found to be equal, confirming the first law. By bending the paper (Activity 10.5), we find that if these three are not in the same plane, reflection does not occur, verifying the second law.

3. How do convex and concave lenses differ in their effect on parallel beams of light? Support your answer with an activity.

Answer: Activity 10.10 shows that when a parallel beam of light passes through a convex lens, it converges to a point (focus). When it passes through a concave lens, the beam diverges outward. Thus, convex lenses are converging lenses while concave lenses are diverging lenses. This is used in applications like magnifying glasses for convex lenses and spectacles for concave lenses.

4. Draw neat diagrams to show the uses of concave and convex mirrors in daily life.

Answer: Concave mirrors are used in torches, headlights of vehicles, and by dentists for seeing large images of teeth (see textbook Fig. 10.6). Convex mirrors are used as side-view mirrors in vehicles, at road intersections for a wider field of view, and for security purposes (see textbook Fig. 10.7).

NCERT Solutions for Class 8 Science Chapter 10: Light: Mirrors and Lenses (2025-26)

Master the fundamentals of Light: Mirrors and Lenses with concise, stepwise NCERT solutions. Quickly review key differences between concave and convex mirrors and lenses to boost your understanding for exams.

Learning how different mirrors and lenses form images helps you answer questions confidently. Using these NCERT Class 8 Science solutions (2025-26), you'll strengthen your conceptual clarity and score well in tests.

Practice drawing diagrams and remember the laws of reflection. Regularly revise definitions and uses of spherical mirrors and lenses for higher marks and better exam strategies.