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I. Chapter Summary

This chapter focuses on the behavior of light when it reflects from mirrors and refracts through lenses. It introduces the laws of reflection and refraction, explains image formation by spherical mirrors and lenses, and teaches students how to use ray diagrams and mirror/lens formulas to solve numerical problems. Real-life applications such as rear-view mirrors, spectacles, and optical instruments are also covered.

II. Key Concepts Covered

Concept	Explanation
Reflection of Light	Bouncing back of light from a surface. Governed by the laws of reflection.
Spherical Mirrors
– Concave: Converges light
– Convex: Diverges light
Used in torch lights, rear-view mirrors.
Image Formation by Spherical Mirrors	Dependent on object position; can be real/inverted or virtual/upright.
Mirror Formula	$1f=1v+1ufrac{1}{f} = frac{1}{v} + frac{1}{u}f1​=v1​+u1​$ (with sign conventions)
Magnification (Mirrors)	$M=hiho=−vuM = frac{h_i}{h_o} = frac{-v}{u}M=ho​hi​​=u−v​$
Refraction of Light	Bending of light when it passes from one medium to another.
Laws of Refraction
1. Incident ray, refracted ray, and normal lie in the same plane
2. Snell’s Law: $frac{sin i}{sin r} = text{constant} = mu$
Refractive Index	μ=Speed of light in vacuumSpeed of light in mediummu $= frac{text{Speed of light in vacuum}}{text{Speed of light in medium}}$ μ=Speed of light in mediumSpeed of light in vacuum​
Lenses
– Convex: Converging lens
– Concave: Diverging lens
Lens Formula	$1f=1v−1ufrac{1}{f} = frac{1}{v} – frac{1}{u}f1​=v1​−u1​$
Magnification (Lenses)	$M=hiho=vuM = frac{h_i}{h_o} = frac{v}{u}M=ho​hi​​=uv$​

III. Important Questions

(A) Multiple Choice Questions (1 Mark)

1. Which of the following mirrors is used in a car’s rear-view mirror?
   a) Plane
   b) Convex ✅ (PYQ 2021)
   c) Concave
   d) None of these
2. The refractive index of a medium is 1.5. What is the speed of light in the medium? (Speed of light in vacuum = 3×1083 × 10^83×108 m/s)
   a) $2 times 10^8 , text{m/s}$✅
   b) $1.5 times 10^8 , text{m/s}$
   c) $3 times 10^8 , text{m/s}$
   d) $1 times 10^8 , text{m/s}$
3. Which lens is used to correct myopia?
   a) Convex
   b) Concave ✅
   c) Plane
   d) None of the above
4. If the image formed by a concave mirror is real and inverted, where is the object placed?
   a) Between pole and focus
   b) Between focus and center of curvature ✅
   c) At focus
   d) Beyond center of curvature

(B) Short Answer Questions (2/3 Marks)

1. Draw a ray diagram for an object placed at the center of curvature of a concave mirror.
2. Define the refractive index. What is its unit?
3. Differentiate between real and virtual images.
4. An object is placed 10 cm from a convex mirror of focal length 15 cm. Find the image position.

(C) Long Answer Questions (5 Marks)

1. State and explain the laws of reflection and refraction. Draw diagrams to support your explanation.
2. Derive the mirror formula using ray diagram and geometry.
3. An object is placed 20 cm from a concave mirror of focal length 10 cm. Calculate the image distance and magnification. Draw the ray diagram.
4. Describe the image formation by a convex lens when the object is placed:
    a) Beyond 2F
    b) At 2F
    c) Between F and 2F
    Draw diagrams and mention characteristics.

(D) HOTS (Higher Order Thinking Skills)

1. Why do stars appear to twinkle but planets do not? Explain using the concept of refraction.
2. A person sees a virtual, erect and diminished image in a mirror. What type of mirror is it and why is it used?

IV. Key Formulas/Concepts

Formula	Explanation
$1f=1v+1ufrac{1}{f} = frac{1}{v} + frac{1}{u}f1​=v1​+u1​$	Mirror formula (sign convention applies)
$1f=1v−1ufrac{1}{f} = frac{1}{v} – frac{1}{u}f1​=v1​−u1​$	Lens formula
$M=−vuM = frac{-v}{u}M=u−v​ (mirror)$, $M=vuM = frac{v}{u}M=uv​ (lens)$	Magnification formulas
$μ=sin⁡isin⁡rmu = frac{sin i}{sin r}μ=sinrsini​$	Snell’s law
$μ=cvmu = frac{c}{v}μ=vc​$	Refractive index as ratio of light speeds

V. Deleted Portions (CBSE 2025–2026)

No portions have been deleted from this chapter as per the rationalized NCERT textbooks.

VI. Chapter-Wise Marks Bifurcation (Estimated – CBSE 2025–2026)

Unit/Chapter	Estimated Marks	Type of Questions Typically Asked
Chapter 9: Light – Reflection and Refraction	10–12 Marks	1 Long Answer, 2–3 Numericals, 1–2 Diagrams

VII. Previous Year Questions (PYQs)

Year	Marks	Question
2021	1	Which mirror is used in the rear-view mirror of vehicles? (Convex)
2020	5	An object is placed at 20 cm from a concave mirror with focal length 10 cm. Find the image and magnification.
2019	3	State laws of refraction. What is refractive index?
2018	2	Differentiate between concave and convex mirrors with diagrams.

VIII. Real-World Application Examples to Connect with Topics

Application	Description
Rear-view mirrors	Convex mirrors provide wider field of view.
Magnifying glasses	Convex lenses form enlarged virtual images.
Camera lenses, projectors	Use converging lenses to form real images.
Eyeglasses for myopia/hypermetropia	Use concave/convex lenses to correct vision.
Microscopes and telescopes	Combine mirrors and lenses for magnification.

IX. Student Tips & Strategies for Success

Time Management

• Dedicate regular time to solving numericals and drawing ray diagrams.
• Use flashcards for formulas and sign conventions.

Exam Preparation

• Master mirror/lens formula applications.
• Practice labelled ray diagrams (at least one for each case).
• Solve NCERT + exemplar problems and PYQs.

Stress Management

• Break large concepts (e.g., image formation) into case-based flowcharts.
• Revise sign conventions using visuals.

X. Career Guidance & Exploration (Class-Specific)

For Classes 9–10

Streams

• Science: Physics, Optometry, Engineering
• Commerce: Optical Instrument Sales/Marketing
• Arts: Product Photography, Industrial Design

Career Paths

• Physicist, Optometrist, Optical Engineer, Camera Lens Designer

Exams

• NTSE, Junior Science Olympiad, NSO, KVPY (Class 11+)

XI. Important Notes

• Always refer to https://ncert.nic.in and https://cbseacademic.nic.in for updates.
• Focus on concept clarity, not just memorization.
• Learn the sign conventions thoroughly to avoid errors in numericals.
• Label diagrams clearly in the exam—this fetches extra marks.