Chapter 9 of Class 10 Science, titled Light – Reflection and Refraction, introduces the core physics concepts behind how light behaves when it encounters different surfaces and mediums. This chapter explains how mirrors and lenses work, covers the laws of reflection and refraction, and shows how to draw ray diagrams. Understanding these basics is crucial for solving numerical problems and real-life applications like how spectacles, cameras, or car mirrors function.
I’m writing this article because this chapter was one of the trickiest when I studied Class 10 Science. Many students struggle with drawing ray diagrams correctly and applying formulas like the mirror and lens equations. That’s why having the official NCERT PDF of Chapter 9 is useful. It’s designed with simple explanations, neat diagrams, and standard questions that often appear in board exams. This chapter is also a building block for Physics in higher classes, especially for students planning to take science in Class 11. So whether you’re revising before exams or just trying to grasp the basic principles of light, this PDF is worth keeping handy.
What You Will Learn in Chapter 9: Light – Reflection and Refraction
Laws of Reflection of Light
- Incident ray, reflected ray and normal
- Angle of incidence = angle of reflection
- Characteristics of images formed by plane mirrors
Spherical Mirrors
- Types: Concave and Convex mirrors
- Uses in daily life (e.g. shaving mirrors, rear-view mirrors)
- Key terms: Pole, centre of curvature, principal axis, focus, radius of curvature
- Ray diagrams for image formation using spherical mirrors
- Mirror formula:
1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}f1=v1+u1 - Sign convention and solving numerical problems
Refraction of Light
- What happens when light travels from one medium to another
- Rules of refraction
- Refractive index and Snell’s law
n=sinisinrn = \frac{\sin i}{\sin r}n=sinrsini - Real-life examples like a coin appearing raised in water
Lenses and Image Formation
- Convex and concave lenses
- Focal length, optical centre, and principal axis
- Ray diagrams for convex and concave lenses
- Lens formula:
1f=1v−1u\frac{1}{f} = \frac{1}{v} – \frac{1}{u}f1=v1−u1 - Power of a lens and its unit (dioptre)
This chapter also includes plenty of solved examples and exercises at the end to help you practise.
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Click here to download NCERT Class 10 Science Chapter 9: Light – Reflection and Refraction PDF
