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CBSE Class 10 Science Chapter 9 Light — Reflection and Refraction Worksheet with Answers

Light — Reflection and Refraction is one of the highest-weightage chapters in CBSE Class 10 Science, contributing roughly 7-8 marks in the board exam. Mastery demands fluency with sign conventions, ray diagrams for spherical mirrors and lenses, numerical problems using the mirror formula and lens formula, and a clear grasp of refraction laws and refractive index. This worksheet offers targeted practice across all question types that appear in the CBSE board paper, complete with fully worked answers.

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Key takeaways

  • ✓Covers all NCERT topics: reflection by spherical mirrors, mirror formula, refraction laws, refractive index and lens formulae for Class 10 Science Chapter 9.
  • ✓40+ graded questions — MCQs, fill-ups, match-the-following, short answers (2-3 marks), long answers (5 marks) and one case-study.
  • ✓Complete answer key with explanations ensures students can self-assess and learn from mistakes without teacher dependency.
  • ✓Suggested time: 90 minutes; Difficulty: Moderate to Challenging — ideal for pre-board and term-end practice.
  • ✓Printable A4 format, suitable for classroom tests, home practice and quick revision before CBSE board exams.
  • ✓Includes HOTS (Higher Order Thinking Skills) questions and numerical problems on mirror formula (1/v + 1/u = 1/f) and lens formula.
  • ✓Case-study question tests application of refraction and lens concepts in real-world optical instrument scenarios.

Quick Chapter Recap: Light — Reflection and Refraction

Chapter 9 in NCERT Class 10 Science introduces two foundational phenomena of light. Reflection by spherical mirrors (concave and convex) follows the mirror formula 1/f = 1/v + 1/u, where f is focal length, v is image distance and u is object distance. Sign convention: distances measured against the direction of incident light are negative. Magnification m = -v/u = h'/h. Refraction occurs when light enters a different medium; Snell's law states n₁ sin i = n₂ sin r. Refractive index n = c/v = (real depth)/(apparent depth). Lenses (convex and concave) obey the lens formula 1/f = 1/v - 1/u and power P = 1/f (in metres), measured in dioptres. Understanding ray diagrams, sign conventions and step-by-step numerical substitution is non-negotiable for scoring full marks in both theory and numerical problems.
  • Mirror formula: 1/f = 1/v + 1/u; magnification m = -v/u.
  • Concave mirror: f < 0; can form real or virtual images. Convex mirror: f > 0; always virtual, erect, diminished.
  • Refraction: light bends towards normal when entering denser medium (n₂ > n₁); away from normal in rarer medium.
  • Lens formula: 1/f = 1/v - 1/u; power P = 1/f (m); 1 D = 1 m⁻¹.
  • Convex lens: converges light, f > 0. Concave lens: diverges light, f < 0.

Section A: Multiple Choice Questions (1 mark each)

This section contains six MCQs testing quick recall of definitions, formulae and conceptual clarity. Each question has four options; select the single best answer. Topics span mirror formula, magnification, refractive index, power of lenses and basic ray optics. Practise under timed conditions to simulate board exam pressure. Write your answers on a separate sheet before checking the answer key at the end of this worksheet. MCQs are a staple in CBSE Class 10 Science board papers, typically carrying 1 mark each and demanding precision rather than lengthy working. Mastering these builds confidence and saves time for longer numerical problems later in the exam.
  • Q1. The focal length of a concave mirror is 15 cm. An object is placed 30 cm in front of it. The image distance v is:
  • (a) +30 cm (b) -30 cm (c) +15 cm (d) -15 cm
  • Q2. A ray of light travelling in air enters obliquely into water. It will:
  • (a) bend away from the normal (b) bend towards the normal (c) not bend (d) reflect back completely
  • Q3. The power of a lens is -2.5 D. Its focal length is:
  • (a) +40 cm (b) -40 cm (c) +2.5 m (d) -2.5 m
  • Q4. A convex mirror always forms an image that is:
  • (a) real and inverted (b) virtual, erect and diminished (c) real and enlarged (d) virtual and enlarged
  • Q5. If magnification m = -1, the image is:
  • (a) same size, virtual (b) same size, real and inverted (c) enlarged (d) diminished
  • Q6. Refractive index of glass with respect to air is 1.5. The speed of light in glass is approximately:
  • (a) 3×10⁸ m/s (b) 2×10⁸ m/s (c) 1.5×10⁸ m/s (d) 4.5×10⁸ m/s

Section B: Fill in the Blanks (1 mark each)

Complete each sentence with the correct term, formula or numerical value. This section tests precision in terminology — CBSE examiners award marks only for exact NCERT language. Read each statement carefully and write your answer in the space provided. Topics include laws of reflection, refractive index, sign convention, lens types and the relationship between power and focal length. Five questions follow. Use your NCERT Class 10 Science textbook glossary if you are unsure of any term during revision, but attempt this worksheet first without notes to gauge your retention honestly.
  • Q7. The angle of incidence is always ________ to the angle of reflection.
  • Q8. The SI unit of power of a lens is ________, symbol ________.
  • Q9. A concave lens always forms a ________, ________ and ________ image.
  • Q10. The reciprocal of focal length in metres is called the ________ of the lens.
  • Q11. When light travels from a rarer to a denser medium, it bends ________ the normal.

Section C: Match the Following & True/False (1 mark each)

Part I: Match each item in Column A with the correct entry in Column B. Write the matching pair (for example, 1-d, 2-a) on your answer sheet. Part II: State whether each statement is True or False. If False, rewrite the statement correctly in your answer key practice. This section consolidates understanding of mirror types, lens behaviour and the physical meaning of positive and negative focal lengths under the New Cartesian Sign Convention adopted by NCERT. Accuracy here directly translates to marks in the board exam, where even a single-word error can cost you a full mark.
  • Part I: Match the Following
  • Column A: (1) Concave mirror (2) Convex lens (3) Refractive index (4) Power +5D
  • Column B: (a) Converging lens (b) Diverging mirror (c) n = c/v (d) Converging mirror (e) f = +20 cm
  • Part II: True or False
  • Q12. A convex mirror can form a real image. (True / False)
  • Q13. The focal length of a concave lens is positive. (True / False)
  • Q14. Magnification is negative for real, inverted images. (True / False)

Section D: Short Answer Questions (2-3 marks each)

Answer each question in 30-50 words or through a labelled ray diagram where specified. CBSE Class 10 Science board papers allocate 2 or 3 marks to questions that test definition recall, formula statement, derivation outline or a single-step numerical. Show all working for numerical problems: write the given data, formula, substitution and final answer with correct units and sign. Five questions follow, spanning reflection by spherical mirrors, refraction laws, refractive index calculations and lens properties. Practice writing concise, point-form answers to save time in the exam hall. Each mark typically corresponds to one distinct point or calculation step, so structure your response accordingly.
  • Q15. State the laws of reflection. (2 marks)
  • Q16. Define refractive index of a medium. Write its formula and SI unit. (2 marks)
  • Q17. A concave mirror has a focal length of 20 cm. An object is placed 40 cm from the mirror. Calculate the image distance and magnification. (3 marks)
  • Q18. Differentiate between a real image and a virtual image with one example of each. (2 marks)
  • Q19. Draw a labelled ray diagram to show the formation of an image by a convex lens when the object is placed between F and 2F. State the nature, position and size of the image. (3 marks)

Section E: Long Answer & HOTS Questions (5 marks each)

These three questions demand multi-step reasoning, derivation or application of concepts to novel scenarios. Allocate roughly 5-7 minutes per question in the exam. HOTS (Higher Order Thinking Skills) problems may combine mirror formula, lens formula and real-world optics (e.g. corrective lenses, optical instruments). Structure your answer with clear sub-headings: (i) Given data, (ii) Formula, (iii) Step-by-step working, (iv) Final answer with interpretation. Diagrams earn method marks even if the numerical answer is incorrect, so never skip the ray diagram when asked. These questions mirror the 5-mark problems in the CBSE Class 10 board paper and separate average scorers from top performers.
  • Q20. Derive the mirror formula 1/f = 1/v + 1/u for a concave mirror using a ray diagram. State the sign convention used. (5 marks)
  • Q21. A convex lens of focal length 15 cm forms an image at a distance of 30 cm on the other side of the lens. (i) Calculate the object distance. (ii) Calculate the magnification. (iii) State the nature, position and size of the image. Draw a ray diagram. (5 marks)
  • Q22. HOTS: A student suffering from myopia can see clearly only up to 2 m. (i) Name the type of lens required to correct this defect. (ii) Calculate the power of the lens needed. (iii) Explain with a ray diagram how the lens corrects the defect. (5 marks)

Section F: Case-Study Question (4 marks)

Case-study questions are a recent addition to the CBSE Class 10 board pattern, introduced from 2020-21 onwards. A short scientific or real-world passage is followed by 3-4 sub-questions (MCQ or very short answer). Read the passage carefully, underline key data (focal lengths, distances, refractive indices) and apply Chapter 9 concepts to answer. This format tests comprehension and application rather than rote memory. The passage below describes an optical instrument scenario; answer the four sub-questions that follow. Each correct answer fetches 1 mark. Write answers on your sheet before consulting the answer key at the end.

Complete Answer Key with Explanations

Below are the fully worked answers for every question in this worksheet. Each MCQ and fill-in-the-blank answer includes a brief justification rooted in NCERT Class 10 Science Chapter 9 terminology. For numerical problems, substitution steps and sign-convention notes are provided so you understand not just what the answer is, but why it is correct. Short- and long-answer model responses follow the CBSE marking scheme: one mark per distinct point or step. Use this key to self-assess, identify weak areas and revise targeted sections before your board exam. If you consistently struggle with lens formula problems, spend extra time on NCERT Examples 9.3 and 9.4. If ray diagrams feel uncertain, redraw Figures 9.8, 9.12 and 9.14 from the textbook until the construction becomes automatic. Remember, CBSE awards partial marks for correct method even if the final answer is wrong — so always show your working in the exam hall. For instant photo-upload doubt solving and 24×7 AI-tutor support across all chapters of Class 10 Science, explore CBSETUTOR.ai at a flat ₹999/month with a 3-day free trial. One subscription covers every subject and class (6-12), making it far more economical than city coaching centres while offering the same depth of explanation anytime, anywhere.
  • Section A Answers:
  • A1. (b) -30 cm. Using 1/f = 1/v + 1/u: 1/(-15) = 1/v + 1/(-30) → 1/v = -1/15 + 1/30 = -1/30 → v = -30 cm.
  • A2. (b) bend towards the normal. Water is denser (higher refractive index) than air; light bends towards normal on entering denser medium.
  • A3. (b) -40 cm. P = 1/f(m) → -2.5 = 1/f → f = -1/2.5 = -0.4 m = -40 cm.
  • A4. (b) virtual, erect and diminished. Convex mirrors always form virtual, erect, smaller images between pole and focus.
  • A5. (b) same size, real and inverted. m = -1 means |m|=1 (same size), negative sign indicates real, inverted image.
  • A6. (b) 2×10⁸ m/s. n = c/v → 1.5 = (3×10⁸)/v → v = 3×10⁸/1.5 = 2×10⁸ m/s.
  • Section B Answers:
  • A7. equal
  • A8. dioptre; D
  • A9. virtual, erect, diminished
  • A10. power
  • A11. towards
  • Section C Answers:
  • Part I: 1-d, 2-a, 3-c, 4-e
  • Part II: A12. False (Convex mirror forms only virtual images). A13. False (Focal length of concave lens is negative). A14. True.
  • Section D Answers:
  • A15. (i) Angle of incidence = angle of reflection. (ii) Incident ray, reflected ray and normal lie in the same plane.
  • A16. Refractive index is the ratio of speed of light in vacuum to speed in the medium. Formula: n = c/v. SI unit: no unit (dimensionless) or stated as pure number.
  • A17. Given: f = -20 cm, u = -40 cm. 1/f = 1/v + 1/u → 1/(-20) = 1/v + 1/(-40) → 1/v = -1/20 + 1/40 = -1/40 → v = -40 cm. m = -v/u = 1. Image real, inverted, same size.
  • A18. Real image: formed by actual convergence of light rays, can be caught on screen (e.g. image in cinema projector). Virtual image: formed by apparent divergence, cannot be projected (e.g. image in plane mirror).
  • A19. [Diagram: Object AB between F and 2F on left of convex lens; rays converge beyond 2F on right.] Image: real, inverted, magnified, formed beyond 2F.
  • Section E Answers:
  • A20. [Diagram: concave mirror, object beyond C, rays reflect to form real inverted image between C and F.] Derivation uses similar triangles from ray geometry: Δ A'B'F ~ Δ CDF and Δ ABP ~ Δ A'B'P, leading to 1/f = 1/v + 1/u. Sign convention: New Cartesian — left of pole negative, right positive; measured from pole along principal axis.
  • A21. (i) 1/f = 1/v - 1/u → 1/15 = 1/30 - 1/u → 1/u = -1/30 → u = -30 cm. (ii) m = v/u = 30/(-30) = -1. (iii) Real, inverted, same size, at 2F. [Diagram: object at 2F left, image at 2F right.]
  • A22. (i) Concave lens (diverging). (ii) Far point = 2 m; corrective lens must form virtual image at 2 m of object at infinity → v = -200 cm, u = ∞. 1/f = 1/v - 1/u = 1/(-200) - 0 = -1/200 → f = -200 cm = -2 m. P = 1/f = -0.5 D. (iii) [Diagram: parallel rays diverge after concave lens; appear to come from far point 2 m, now within normal near point range.]
  • Section F Answers:
  • A23. (b) Real and inverted (all camera/projector images are real, inverted).
  • A24. (b) 25 cm. 1/20 = 1/v - 1/(-100) → 1/v = 1/20 - 1/100 = 4/100 = 1/25 → v = 25 cm.
  • A25. (b) F (focal point). Object at infinity → image at focus.
  • A26. (b) shorter focal length (wider field of view needs lower f, higher power).

How to Use This Worksheet Effectively

Print this worksheet on A4 paper and attempt it under exam conditions — no textbook, no phone, 90 minutes on the clock. Use a pencil for diagrams and a pen for written answers so you simulate board exam pressure. After completing all sections, spend 20 minutes checking your answers against the key provided here. Award yourself marks honestly: 1 mark per correct MCQ, fill-up or match item; 2-3 marks per short answer based on completeness; 5 marks per long answer if method, working and conclusion are all correct. A score above 70 per cent indicates strong readiness for Chapter 9 in the board exam. Between 50-70 per cent means concept gaps — revise NCERT Examples and try the worksheet again after two days. Below 50 per cent signals the need for guided help: consider watching video solutions on CBSETUTOR.ai or booking a doubt-clearing session with your school teacher. Repeat similar worksheets every week during your revision phase to build speed and accuracy. Keep a separate error log: write down every mistake, the correct answer and the concept involved. Review this log the night before your Science board paper for a quick confidence boost and last-minute clarity.
  • Attempt the worksheet in one sitting under timed conditions (90 minutes).
  • Use NCERT sign convention strictly: measure all distances from the pole/optical centre.
  • For numericals, write Given, Formula, Substitution, Answer with unit — each step earns marks.
  • Ray diagrams must be neat, labelled (P, F, C, object, image) and drawn to approximate scale.
  • Self-assess using the answer key; identify weak topics and revise NCERT Examples 9.1-9.5.
  • Repeat the worksheet after one week to check retention and improvement in speed.

Common Mistakes Students Make in Chapter 9 and How to Avoid Them

CBSE examiners report recurring errors year after year in Light — Reflection and Refraction questions. First, incorrect sign convention: forgetting that object distance u and focal length f of concave mirrors and concave lenses are always negative. Second, formula confusion: swapping mirror formula (1/f = 1/v + 1/u) with lens formula (1/f = 1/v - 1/u). Third, ray diagram sloppiness: drawing unsharpened rays that do not pass through F or C, or omitting arrowheads. Fourth, unit mismatches: mixing centimetres and metres in power calculations without converting. Fifth, incomplete answers: writing just the formula without substitution or skipping the statement of image nature (real/virtual, erect/inverted, magnified/diminished). Avoid these pitfalls by practicing 10-15 numericals from NCERT and exemplar, labelling every ray diagram component and double-checking signs before substitution. Create a one-page formula sheet with sign conventions prominently highlighted and revise it daily in the week before your board exam.
  • Always apply New Cartesian Sign Convention: distances against incident light direction are negative.
  • Write the correct formula first, then substitute — do not calculate mentally and write only the answer.
  • In ray diagrams, use a sharp pencil, ruler and clearly mark P (pole), F (focus), C (centre of curvature).
  • Convert all distances to the same unit (preferably cm) before substituting into formulae.
  • State image characteristics explicitly: real or virtual, erect or inverted, magnified/diminished/same size.
  • For power problems, remember P (dioptre) = 1/f (metre); convert cm to m before calculating.
  • Read the question carefully: 'in front of' means negative u; 'behind the mirror' means positive (for mirrors).

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Frequently asked questions

What is the mirror formula for Class 10 Science Chapter 9?+
The mirror formula is 1/f = 1/v + 1/u, where f is focal length, v is image distance and u is object distance. All measurements use the New Cartesian Sign Convention: distances measured against the direction of incident light are negative.
How is the lens formula different from the mirror formula?+
The lens formula is 1/f = 1/v - 1/u (note the minus sign), while the mirror formula is 1/f = 1/v + 1/u. This distinction is critical in CBSE exams; mixing them results in incorrect numerical answers and loss of marks.
What is the New Cartesian Sign Convention used in NCERT Class 10 Science?+
All distances are measured from the pole (for mirrors) or optical centre (for lenses) along the principal axis. Distances in the direction of incident light are positive; distances against it are negative. Heights above the axis are positive; below are negative.
How many marks does Chapter 9 carry in the CBSE Class 10 Science board exam?+
Light — Reflection and Refraction typically carries 7-8 marks, distributed among MCQs (1 mark), short answers (2-3 marks), one long numerical or derivation (5 marks) and often appears in the case-study section (4 marks).
What is the formula for magnification in mirrors and lenses?+
For mirrors: m = -v/u = h'/h. For lenses: m = v/u = h'/h. A negative magnification indicates a real, inverted image; positive magnification means virtual and erect.
How do I draw ray diagrams accurately for spherical mirrors?+
Use a ruler and sharp pencil. Mark the pole P, focus F and centre of curvature C on the principal axis. Draw at least two of these rays: (i) parallel to axis, reflects through F; (ii) through F, reflects parallel; (iii) through C, reflects back. Where rays meet (or appear to meet) is the image position.
What is refractive index and how is it calculated?+
Refractive index n of a medium is the ratio of the speed of light in vacuum (c) to the speed in the medium (v): n = c/v. It is dimensionless. For two media, Snell's law is n₁ sin i = n₂ sin r.
Why is the focal length of a concave mirror negative?+
Under the New Cartesian Sign Convention, the focus of a concave mirror lies in front of the mirror (on the same side as the object), which is against the direction of incident light. Therefore f is taken as negative.
What is the power of a lens and its unit?+
Power P = 1/f, where f is focal length in metres. The SI unit is dioptre (D); 1 D = 1 m⁻¹. A convex lens has positive power; a concave lens has negative power.
How can I improve my speed in solving numerical problems on lenses and mirrors?+
Practice 10-15 NCERT in-text and end-of-chapter numericals daily. Write the formula first, list given data with correct signs, substitute step-by-step and state the final answer with unit. Use CBSETUTOR.ai for instant step-by-step solutions and personalized practice worksheets to build confidence and speed before the board exam.

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