TEACHGYAN • CLASS 10 SCIENCE • NCERT 2026–27
Chapter 9: Light – Reflection and Refraction
Detailed Notes • Diagrams • Experiments • Competency • Board Practice
📖 Chapter Explanation
Light travels in straight lines in a uniform medium, but its direction can change through reflection and refraction. The chapter develops ray diagrams, mirror and lens conventions, image formation and numerical relationships.
🧭 Concept Map
🔬 Core Science
For spherical mirrors, 1/f=1/v+1/u and magnification m=−v/u. For lenses, 1/f=1/v−1/u and m=v/u, using the Cartesian sign convention consistently.
🖼️ Diagram to Draw
Use a labelled textbook-style diagram with arrows, direction of travel and key parts.
💡 Worked/Applied Example
For spherical mirrors, 1/f=1/v+1/u and magnification m=−v/u. For lenses, 1/f=1/v−1/u and m=v/u, using the Cartesian sign convention consistently.
⚠️ Common Errors
A concave mirror can form different types of images depending on object position. Ray diagrams are not decoration: they provide a geometric explanation of image location and nature.
🧠 Concept-Based MCQs
- An object is placed before a convex lens. Students draw the principal rays, determine the image position for a specified object location and describe the image.
Answer Key: 1-B, 2-A, 3-A, 4-B.
📊 Case-Based / Competency
A frequent error is mixing mirror and lens sign conventions or using the wrong formula. Draw a labelled ray diagram before substituting numbers.
- Identify the scientific concept involved.
- Draw/interpret the required diagram or model.
- Apply the principle step by step.
- Explain and verify the conclusion.
🔎 Extension Case
The angle of incidence equals the: A) angle of refraction B) angle of reflection C) focal angle D) critical angle always|A convex lens is generally: A) converging B) diverging C) opaque D) plane only|Mirror formula is: A) 1/f=1/v+1/u B) 1/f=1/v−1/u C) f=u+v D) f=uv|A concave mirror can form a real image when the object is: A) always at pole B) in suitable positions beyond focus C) only behind mirror D) nowhere
🧪 Activity / Observation Corner
Design a safe classroom observation related to this chapter. Record the materials, procedure, observation and inference. Where a practical activity is not suitable, use a labelled diagram or simulation-based observation instead.
🔥 HOTS & Board Challenge
- Explain why the phenomenon occurs rather than only naming it.
- Predict what changes if one variable is altered.
- Find and correct a plausible incorrect explanation.
- Connect the concept with a real-life application.
✍️ Exam Practice
- Define the central concept with an example.
- Answer a diagram-based question.
- Solve a multi-step competency problem.
- Explain an application or experiment.
- Write a complete 5-mark answer with scientific reasoning.
📄 Practice Worksheet
- 5 concept checks
- 5 application questions
- 3 diagram-based questions
- 2 case-based questions
- 2 HOTS questions
- 1 board-style challenge
🎯 One-Minute Revision
ray → reflection → spherical mirror → mirror formula → magnification → refraction → lens → lens formula
🏆 Mastery Checklist
- ☐ I can explain the concept scientifically.
- ☐ I can draw and label the key diagram.
- ☐ I can apply the concept to a new situation.
- ☐ I can answer competency/case-based questions.
- ☐ I can justify my conclusion.
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Original explanatory study material aligned to the current NCERT/CBSE framework; textbook passages are not reproduced verbatim.