NCERT Solutions for Class 8th Science Chapter 10 Light: Mirrors and Lenses
Updated on 2026-09-19
About this chapter
A spherical mirror is a mirror whose reflecting surface is shaped like a part of a hollow sphere. If it curves inwards it is a concave mirror ; if it curves outwards it is a convex mirror . A concave mirror gives an image that is enlarged, diminished or the same size, and erect or inverted, depending on how far the object is from the mirror. A convex mirror always gives an erect, diminished image. Two laws of reflection: (i) the angle of incidence equals the angle of reflection, and (ii) the incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane. Both angles are measured from the normal . The laws hold for every mirror — plane, concave and convex. Because a spherical surface is curved, the normal points a different way at each point, so a parall
- Chapter opener
- .1 What Are Spherical Mirrors?
- .2 Characteristics of Images Formed by Spherical Mirrors
- .3 What Are the Laws of Reflection?
- .4 What Is a Lens?
- End-of-chapter questions
- Extension tasks
Quick revision
| Term | What it means | Key behaviour | Where you meet it |
|---|---|---|---|
| Spherical mirror | A mirror whose reflecting surface is a part of a hollow sphere | The normal points a different way at each point of the surface | Concave and convex mirrors |
| Concave mirror | Reflecting surface curves inwards | Converges a parallel beam to a point F | Torch reflector, vehicle headlight, dentist's mirror |
| Convex mirror | Reflecting surface curves outwards | Diverges a parallel beam; image always erect and diminished | Side-view mirror, road-safety mirror, shop surveillance mirror |
| Incident ray | The ray of light that falls on the mirror | Meets the mirror at the point of incidence, O | Fig. 10.9a |
| Normal | The line drawn at 90° to the mirror at the point of incidence | Both i and r are measured from it — never from the mirror | Fig. 10.9b |
| Angle of incidence (i) | Angle between the incident ray and the normal | i = r | Table 10.1 |
| Angle of reflection (r) | Angle between the reflected ray and the normal | i = r | Table 10.1 |
| Erect / inverted | Image the same way up as the object / upside down | Convex mirror and concave lens: always erect | Fig. 10.5, Fig. 10.17 |
| Enlarged / diminished | Image larger / smaller than the object | Convex mirror and concave lens: always diminished | Fig. 10.23, Fig. 10.24 |
| Lateral inversion | Left and right interchanged in the image | Seen in plane, concave and convex mirrors alike | Activity 10.3 |
| Convex lens | Transparent piece thicker at the middle than at the edges | Converging lens; can burn paper in sunlight | Magnifying glass, camera, the lens of our eye |
| Concave lens | Transparent piece thicker at the edges than at the middle | Diverging lens; image always erect and diminished | Some spectacle lenses, viewfinders |
Exercises
- Chapter opener — Probe and ponder Page 152
- .1 What Are Spherical Mirrors? — Activity 10.1: Let us explore Page 15310
- .1 What Are Spherical Mirrors? — Activity 10.2: Let us distinguish Page 15510
- .1 What Are Spherical Mirrors? — In-text Questions Page 15510
- .2 What Are the Characteristics of Images Formed by Spherical Mirrors? — Activity 10.3: Let us explore Page 15510
- .2 Characteristics of Images Formed by Spherical Mirrors — In-text Questions Page 15610
- .2 Characteristics of Images Formed by Spherical Mirrors — A step further Page 15610
- .3 What Are the Laws of Reflection? — In-text Questions Page 15710
- .3 What Are the Laws of Reflection? — Activity 10.4: Let us experiment Page 15710
- .3 What Are the Laws of Reflection? — In-text Questions Page 15810
- .3 What Are the Laws of Reflection? — Activity 10.5: Let us experiment Page 15910
- .3 What Are the Laws of Reflection? — In-text Questions Page 16010
- .3 What Are the Laws of Reflection? — Activity 10.6: Let us explore Page 16010
- .3 What Are the Laws of Reflection? — In-text Questions Page 16110
- .3 What Are the Laws of Reflection? — Activity 10.7: Let us explore Page 16110
- .3 What Are the Laws of Reflection? — A step further Page 16110
- .4 What Is a Lens? — In-text Questions Page 16210
- .4 What Is a Lens? — Activity 10.8: Let us explore Page 16210
- .4 What Is a Lens? — In-text Questions Page 16310
- .4 What Is a Lens? — Activity 10.9: Let us experiment Page 16310
- .4 What Is a Lens? — In-text Questions Page 16410
- .4 What Is a Lens? — Activity 10.10: Let us investigate Page 16410
- .4 What Is a Lens? — Activity 10.11: Let us investigate Page 16510
- .4 What Is a Lens? — In-text Questions Page 16510
- End-of-chapter questions — Keep the curiosity alive Page 166
- Extension tasks — Discover, design, and debate Page 169