Class 10 Science Chapter 9: Light – Reflection and Refraction – NCERT Solutions Notes Light – Reflection and Refraction is an important Physics chapter in Class 10 Science. It explains how light behaves when it reflects from surfaces and refracts while passing through different media. It also introduces mirrors, lenses, and image formation. These notes are designed for clear understanding and NCERT-based revision. Key Concepts Light Light is a form of energy that enables us to see objects. Reflection of Light Reflection is the bouncing back of light when it strikes a surface. Laws of Reflection Angle of incidence = Angle of reflection Incident ray, reflected ray, and normal lie in the same plane Mirrors Types of Mirrors Plane mirror Concave mirror Convex mirror Image Formation by Mirrors Concave Mirror Can form real and virtual images Used in torches, headlights, shaving mirrors Convex Mirror Always forms virtual, erect, and diminished images Used in rear-view mirrors Mirror Formula 1/f = 1/v + 1/u Where: f = focal length v = image distance u = object distance Magnification m = height of image / height of object = v/u Refraction of Light Refraction is the bending of light when it passes from one medium to another. Laws of Refraction (Snell’s Law) n₁ sin i = n₂ sin r Refractive Index It measures how much light bends in a medium. n = speed of light in vacuum / speed of light in medium Lenses Types of Lenses Convex lens (converging) Concave lens (diverging) Image Formation by Lenses Convex Lens Can form real and virtual images Used in cameras, magnifying glasses Concave Lens Always forms virtual, erect, and diminished images Lens Formula 1/f = 1/v – 1/u Magnification (Lens) m = v/u Power of Lens P = 1/f (in meters) Unit: Dioptre (D) NCERT Important Concepts Real Image Formed by actual intersection of light rays Can be captured on screen Virtual Image Formed when rays appear to meet Cannot be captured on screen NCERT Important Questions (Concept Based) What is reflection? Bouncing back of light from a surface. What is refraction? Bending of light when it passes from one medium to another. Why does a pencil look bent in water? Due to refraction of light. Important Diagrams to Revise Ray diagram for concave mirror Ray diagram for convex mirror Lens ray diagrams Refraction through glass slab Why this chapter is important This chapter is highly scoring and very important for exams. It is frequently asked in: Ray diagrams Numericals (mirror and lens formula) Concept-based questions NCERT exercises Final Revision Tip Focus on: Ray diagrams (very important) Mirror and lens formulas Difference between real and virtual image Refraction and refractive index