💡 CBSE · Class 10 · Science · Chapter 10

Light: Reflection
and Refraction

Complete chapter resources for CBSE Class 10 Science — topic breakdown, key formulas, sample questions, previous year board questions, and instant AI question paper generation.

5Topics
5–7Board marks
8Sample questions
3PYQ included

Free for independent teachers · No credit card required

Key Formulas — Chapter 10
  • Mirror formula: 1/f = 1/v + 1/u
  • Magnification (mirror): m = −v / u = h' / h
  • Snell's Law: n = sin i / sin r
  • Lens formula: 1/f = 1/v − 1/u
  • Lens power: P = 1 / f(m) [unit: dioptre D]
  • Refractive index: n = c / v

What this chapter covers

Light: Reflection and Refraction is one of the highest-weightage chapters in CBSE Class 10 Science. It begins with the nature of light and the laws of reflection — angle of incidence equals angle of reflection — and applies them to spherical mirrors (concave and convex). Students learn to draw ray diagrams, locate images for different object positions, and calculate image distance, object distance, and focal length using the mirror formula (1/f = 1/v + 1/u) along with the New Cartesian Sign Convention.

The second half of the chapter deals with refraction of light — the bending of light as it passes from one medium to another due to a change in speed. Snell's Law (n = sin i / sin r) and the concept of refractive index are central here. The chapter then extends refraction to spherical lenses (convex and concave), covering the lens formula (1/f = 1/v − 1/u), magnification, and the power of a lens measured in dioptres. Common daily-life phenomena such as the apparent depth of a pool, a pencil appearing bent in water, and the functioning of the human eye are explained using these principles.

Board questions on this chapter consistently include numerical problems using mirror and lens formulas, ray diagram drawing (typically 2–3 marks), and short-answer questions on sign convention, power of lenses, and refractive index. Students who master the sign convention and can construct accurate ray diagrams for all standard object positions typically secure full marks in this chapter.

What's inside Chapter 10

As per NCERT Class 10 Science (CBSE syllabus)

Topic 1
Reflection of Light & Spherical Mirrors
Laws of reflection, types of spherical mirrors (concave/convex), key terms (pole, centre of curvature, principal axis, focus), relationship f = R/2, and the New Cartesian Sign Convention.
Topic 2
Image Formation by Mirrors & Mirror Formula
Ray diagram construction for concave and convex mirrors at all standard object positions. Mirror formula: 1/f = 1/v + 1/u. Linear magnification m = −v/u. Nature, position, and size of images.
Topic 3
Refraction of Light & Refractive Index
Refraction through a glass slab, laws of refraction, Snell's Law (n = sin i / sin r), absolute and relative refractive index, optical density, and speed of light in different media.
Topic 4
Refraction through Spherical Lenses
Types of lenses (convex/concave), key terms (optical centre, principal focus, focal length), ray diagrams for all standard object positions for convex and concave lenses.
Topic 5
Lens Formula, Magnification & Power of a Lens
Lens formula: 1/f = 1/v − 1/u. Magnification m = v/u = h'/h. Power of a lens P = 1/f (in metres); unit dioptre (D). Combined power of lenses in contact: P = P₁ + P₂ + …

How this chapter fits in

Useful for setting question difficulty and cross-chapter papers.

Builds on
Class 8 · Light (NCERT)
Regular and diffuse reflection, incident/reflected ray, plane mirror images
Class 9 · Motion & Wave basics
Speed, velocity, and wave nature of light as an electromagnetic wave
Chapter 10 Light:
Reflection &
Refraction
Leads to
Ch 11 · Human Eye & Colourful World
Lens in the eye, defects of vision, dispersion and scattering of light
Class 12 · Ray Optics (Physics)
Total internal reflection, optical instruments, wave optics

Marks & question-type breakdown

Typical pattern based on CBSE Class 10 Science board papers from the last five years.

Question type Marks Typical count What's usually tested
MCQ / Assertion–Reason 1 1–2 Nature of image, sign convention, power of lens, refractive index comparison
Very Short Answer 2 1 Define terms, state laws of reflection/refraction, or a short numerical
Short Answer (Numerical / Diagram) 3 1 Mirror or lens formula numerical, or ray diagram with one standard object position
Long Answer / Case-Based 4–5 1 Multi-part: ray diagram + numerical + explain a phenomenon (e.g. apparent depth, power of combination)
Total (approximate) 5–7 4–5 Weightage varies across paper sets and years

8 sample questions — generated by MarksZen AI

Aligned to CBSE Class 10 Science Chapter 10. Covers all question types across Easy, Medium, and Hard difficulty.

Q1 Easy 1 mark MCQ
The focal length of a concave mirror is 15 cm. Its radius of curvature is: (a) 7.5 cm (b) 15 cm (c) 30 cm (d) 45 cm
Q2 Easy 2 marks Short Answer
State the two laws of reflection of light. Which of these laws also applies to refraction?
Q3 Medium 2 marks Numerical
An object is placed 30 cm in front of a concave mirror of focal length 20 cm. Using the mirror formula, find the position of the image. State whether the image is real or virtual.
Q4 Medium 3 marks Diagram + Short Answer
Draw a ray diagram showing the image formed by a convex lens when an object is placed between the optical centre and the principal focus. State the nature, position, and size of the image formed.
Q5 Medium 3 marks Numerical
A ray of light travelling in air enters obliquely into water. The angle of incidence is 45° and the refractive index of water is 1.33. (i) Calculate the angle of refraction (use sin 45° = 0.707). (ii) Does the ray bend towards or away from the normal? Give a reason.
Q6 Hard 4 marks Numerical + Diagram
An object 5 cm tall is placed 25 cm in front of a convex lens of focal length 10 cm. (i) Use the lens formula to find the image distance. (ii) Calculate the magnification. (iii) Find the height of the image. (iv) State whether the image is real or virtual, erect or inverted.
Q7 Hard 4 marks Word Problem
A doctor prescribes spectacles with lenses of power −2.5 D for one eye and +1.5 D for the other. (i) What is the focal length of each lens? (ii) What type of lens (concave or convex) is each? (iii) If the two lenses are placed in contact, what is the combined power and focal length of the combination?
Q8 Hard 5 marks Case-Based
A concave mirror has a radius of curvature of 40 cm. An object is placed 60 cm in front of the mirror. (i) Calculate the focal length of the mirror. (ii) Using the mirror formula, find the image distance. (iii) Calculate the magnification and state the nature of the image. (iv) If the object is now moved to a position 15 cm in front of the mirror (between F and P), describe how the nature of the image changes and explain why.
Generate a full paper with answer key →

MarksZen AI creates a complete question paper with answer key in under 2 minutes.

From CBSE board examinations

Actual questions from past Class 10 Science board papers — Light: Reflection and Refraction chapter.

Board 20223 marks
An object is placed at a distance of 12 cm in front of a concave mirror of radius of curvature 20 cm. Find the position and nature of the image formed. Draw a labelled ray diagram to show the formation of the image. (CBSE All India 2022)
Board 20232 marks
The refractive index of glass is 1.5 and the speed of light in air is 3 × 10⁸ m/s. Calculate the speed of light in glass. Why does a ray of light bend when it passes from one medium to another? (CBSE Delhi 2023)
Board 20205 marks
A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in contact with each other. (a) What is the power of this combination? (b) What is the focal length of this combination? (c) Is the combination converging or diverging? (CBSE 2020)

Create a board-aligned
question paper in 2 minutes.

Pick chapter, set the question-type mix and total marks — MarksZen AI generates the full paper with answer key. CBSE, ICSE, and all State Boards supported.

  • All 5 topics of this chapter
  • MCQ + numericals + diagram-based questions
  • Answer key included
  • PDF export ready
Sign Up Free & Generate →

Questions teachers ask

How many marks does Light: Reflection and Refraction carry in the CBSE Class 10 board exam? +
This chapter typically carries 5–7 marks in the CBSE Class 10 Science board exam, spread across 2–3 questions — one 1-mark MCQ or assertion-reason, one 2-mark short answer on mirror or lens formula, and one 3–5 mark diagram-based or numerical question. It has appeared consistently in every CBSE board paper for the last decade.
What is the mirror formula and how is it used in board exams? +
The mirror formula is 1/f = 1/v + 1/u, where f is the focal length, v is the image distance, and u is the object distance (all measured from the pole). In board exams, students are given two of the three values and asked to find the third. Always apply the New Cartesian Sign Convention: distances measured in the direction of the incident ray are positive, and against the incident ray are negative.
What is Snell's Law and why is it important for board exams? +
Snell's Law states that n1 sin θ1 = n2 sin θ2, where n1 and n2 are the refractive indices of the two media and θ1, θ2 are the angles of incidence and refraction. For CBSE Class 10, the form most used is n = sin i / sin r (ratio form) for a ray going from air into a medium. It appears in 2-mark numerical questions and also as the basis for explaining total internal reflection qualitatively.
What is the difference between a real image and a virtual image, and how does it appear in board questions? +
A real image is formed by actual convergence of reflected or refracted rays and can be projected on a screen; a virtual image is formed by apparent divergence and cannot be projected. Board questions on this distinction typically take the form of ray diagrams (draw the image formed by a concave mirror when the object is at C, or by a convex lens when the object is between F and O). Correctly labelling the image as real/virtual, inverted/erect, and magnified/diminished earns full marks.
How do I generate a custom question paper for Light: Reflection and Refraction using MarksZen? +
Sign up for a free MarksZen account, choose CBSE Class 10 Science, select Chapter 10 (Light: Reflection and Refraction), set your preferred question-type mix (MCQ, short answer, diagram-based, numericals) and total marks — the AI generates a complete board-aligned paper with answer key in under 2 minutes, ready for PDF export.