🌟 Introduction

Light: Reflection and Refraction is one of the most important chapters in the Class 10 CBSE Science syllabus. For students preparing for CBSE Board examinations, solving Previous Year Questions (PYQs) is the most effective way to understand the exam pattern, marking scheme, and frequently repeated themes. At Dhingra Classes Nashik, we have compiled the most important PYQs from this chapter, organized by marks weightage, to help Class 10 students score maximum marks.

This chapter covers Reflection of Light, Laws of Reflection, Plane Mirrors, Spherical Mirrors, Concave Mirrors, Convex Mirrors, Mirror Formula, Magnification, Refraction of Light, Laws of Refraction, Snell’s Law, Refractive Index, Lens Formula, Power of Lens, and Combination of Lenses. These PYQs have been collected from CBSE Board exams across multiple years and are essential for effective board exam preparation.

📚 Why Solving PYQs Is Important for CBSE Class 10

Before diving into the questions, let us understand why Previous Year Questions are crucial for Class 10 CBSE students.

🎯 Benefits of Solving PYQs

• ✅ Understanding Exam Pattern: PYQs reveal how questions are framed

• 📝 Identifying Repeated Themes: Many questions repeat with slight variations

• 🧠 Better Answer Writing: PYQs help practice structured answers

• 🏆 Higher Scores: Familiarity with question types reduces exam stress

• 📊 Time Management: Practice helps allocate time per question correctly

• 🔦 Numerical Practice: Many PYQs require solving numericals using formulas

📖 1 Mark Questions (Very Short Answer Type)

These questions are typically asked as MCQs, Assertion-Reason, or one-line answers. They test factual knowledge and basic understanding.

Set A: MCQs and One-Line Answers

Set B: Assertion-Reason Questions

Question 1: Assertion (A): A convex mirror always forms a virtual, erect, and diminished image. Reason (R): The image formed by a convex mirror is always behind the mirror.
Answer: Both A and R are true and R is the correct explanation of A.

Question 2: Assertion (A): The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in the medium. Reason (R): Light travels slower in a denser medium.
Answer: Both A and R are true and R is the correct explanation of A.

📖 2 Marks Questions (Short Answer Type I)

These questions require two points or brief explanations and are designed to test conceptual understanding.

Question 1: State the two laws of reflection of light.

Answer:

• The angle of incidence is equal to the angle of reflection.

• The incident ray, reflected ray, and normal lie in the same plane.

Question 2: Define the principal focus of a concave mirror.

Answer:

• The principal focus of a concave mirror is the point on the principal axis where rays parallel to the principal axis converge after reflection.

• It lies in front of the mirror.

Question 3: Why do we prefer a convex mirror as a rear-view mirror in vehicles?

Answer:

• A convex mirror gives a wider field of view.

• It always forms an erect and diminished image, making it easier to see traffic behind.

Question 4: What is the magnification of a lens? Write its formula.

Answer:

• Magnification is the ratio of the height of the image to the height of the object.

• Formula: m = h’/h = v/u.

Question 5: Define refractive index of a medium.

Answer:

• The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in the medium.

• It is denoted by n = c/v.

Question 6: What is the power of a lens? Write its SI unit.

Answer:

• The power of a lens is the reciprocal of its focal length in metres.

• SI unit: Dioptre (D).

Question 7: Why does a ray of light bend when it enters from one medium to another?

Answer:

• Light bends due to a change in its speed as it enters a medium with a different optical density.

• This phenomenon is called refraction.

Question 8: What is the difference between a real image and a virtual image?

Answer:

• A real image is formed when rays actually meet and can be obtained on a screen.

• A virtual image is formed when rays appear to meet and cannot be obtained on a screen.

📖 3 Marks Questions (Short Answer Type II)

These questions require detailed explanations with three distinct points and test analytical understanding.

Question 1: An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.

Answer:

• Using mirror formula: 1/v + 1/u = 1/f

• u = -10 cm, f = +15 cm

• 1/v = 1/15 – (-1/10) = 1/15 + 1/10 = (2+3)/30 = 5/30 = 1/6

• v = 6 cm

• The image is formed 6 cm behind the mirror, virtual and erect.

Question 2: A concave mirror produces a three times magnified real image of an object placed at 10 cm in front of it. Where is the image located?

Answer:

• Magnification m = -3 (real image)

• m = -v/u → -3 = -v/(-10) → v = -30 cm

• Using mirror formula: 1/f = 1/v + 1/u = -1/30 – 1/10 = -4/30

• f = -7.5 cm

• The image is located 30 cm in front of the mirror.

Question 3: A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed if the image is equal to the size of the object? Also find the power of the lens.

Answer:

• For equal size image, object is at 2F and image is at 2F.

• So, u = -50 cm, v = +50 cm

• 1/f = 1/v – 1/u = 1/50 – (-1/50) = 2/50 = 1/25

• f = 25 cm = 0.25 m

• Power P = 1/f = 1/0.25 = +4 D

Question 4: Explain the refraction of light through a rectangular glass slab.

Answer:

• When light enters a glass slab, it bends towards the normal (air to glass).

• Inside the glass, it travels straight; when it exits, it bends away from the normal (glass to air).

• The emergent ray is parallel to the incident ray, but displaced laterally.

Question 5: Explain the rules for obtaining images formed by spherical mirrors.

Answer:

• A ray parallel to the principal axis passes through the focus after reflection.

• A ray passing through the focus becomes parallel to the principal axis after reflection.

• A ray passing through the centre of curvature reflects back along the same path.

Question 6: Explain the sign conventions for spherical mirrors.

Answer:

• The object is always placed on the left of the mirror.

• Distances measured in the direction of incident light are positive.

• Distances measured against the direction of incident light are negative.

• Heights above the principal axis are positive; below are negative.

Question 7: Explain the concept of refractive index and its importance.

Answer:

• Refractive index is the ratio of the speed of light in vacuum to the speed of light in the medium.

• It determines how much light bends when entering a medium.

• It is important for designing lenses, prisms, and optical instruments.

Question 8: Explain the formation of images by a concave lens.

Answer:

• A concave lens always forms a virtual, erect, and diminished image.

• The image is formed between the optical centre and the focus.

• It is formed on the same side as the object.

Question 9: Explain the lens formula and magnification for a convex lens.

Answer:

• Lens formula: 1/v – 1/u = 1/f

• Magnification: m = v/u = h’/h

• For a convex lens, f is positive; for a concave lens, f is negative.

Question 10: Explain the power of a lens and its combination.

Answer:

• Power of a lens: P = 1/f (in metres), unit is Dioptre (D).

• For lenses in contact: P = P₁ + P₂ + P₃ + …

• Power is positive for convex lens and negative for concave lens.

Question 11: Explain the difference between reflection and refraction.

Answer:

• Reflection: Light bounces back from a surface; angle of incidence = angle of reflection.

• Refraction: Light bends when passing from one medium to another; speed of light changes.

• Reflection occurs at surfaces, refraction occurs at interfaces.

Question 12: Explain the concept of total internal reflection.

Answer:

• Total internal reflection occurs when light travels from a denser to a rarer medium.

• The angle of incidence must be greater than the critical angle.

• It is used in optical fibres, prisms, and diamonds.

📖 5 Marks Questions (Long Answer Type)

These questions require comprehensive answers with five distinct points and test in-depth understanding and analytical skills.

Question 1: State the laws of reflection. Describe the formation of an image by a concave mirror when the object is placed between the focus and the centre of curvature.

Answer:

• Laws of Reflection:

  • The angle of incidence is equal to the angle of reflection.

  • The incident ray, reflected ray, and normal lie in the same plane.

• Image Formation:

  • When the object is between F and C, the image is formed beyond C.

  • The image is real, inverted, and magnified.

  • Ray diagram: One ray parallel to the principal axis reflects through F; another through C reflects back along the same path.

  • The image is formed where these reflected rays intersect.

Question 2: An object 5 cm tall is placed 25 cm from a convex lens of focal length 10 cm. Find the position, nature, and size of the image.

Answer:

• u = -25 cm, f = +10 cm

• 1/v = 1/f + 1/u = 1/10 – 1/25 = (5-2)/50 = 3/50

• v = 50/3 = 16.67 cm

• Magnification m = v/u = 16.67/(-25) = -0.67

• Image is real, inverted, and diminished.

• Height of image = m × h = -0.67 × 5 = -3.33 cm (inverted).

Question 3: A concave lens has a focal length of 15 cm. At what distance should an object be placed so that it forms an image at 10 cm from the lens? Also find the magnification.

Answer:

• f = -15 cm, v = -10 cm (virtual image for concave lens)

• 1/u = 1/v – 1/f = -1/10 + 1/15 = (-3+2)/30 = -1/30

• u = -30 cm

• Magnification m = v/u = -10/(-30) = +0.33

• Image is virtual, erect, and diminished.

Question 4: Explain the refraction of light through a prism. Draw a ray diagram.

Answer:

• When light passes through a prism, it bends towards the base.

• The angle between the incident ray and emergent ray is called the angle of deviation.

• The prism disperses white light into its component colours.

• Ray diagram: Incident ray enters the prism, refracts at both surfaces, and emerges deviated.

• The refractive index determines the amount of bending.

Question 5: Explain the formation of images by a convex lens for different object positions.

Answer:

• Object at infinity: Image at focus, real, inverted, highly diminished.

• Object beyond 2F: Image between F and 2F, real, inverted, diminished.

• Object at 2F: Image at 2F, real, inverted, same size.

• Object between F and 2F: Image beyond 2F, real, inverted, magnified.

• Object at F: Image at infinity.

• Object between F and O: Image on the same side, virtual, erect, magnified.

Question 6: Explain the mirror formula and magnification for spherical mirrors.

Answer:

• Mirror formula: 1/v + 1/u = 1/f

• Magnification: m = -v/u = h’/h

• Sign conventions: Distances in the direction of incident light are positive; against are negative.

• For concave mirror: f is negative; for convex mirror: f is positive.

• Magnification: Positive for virtual images; negative for real images.

Question 7: Explain the lens formula and its applications.

Answer:

• Lens formula: 1/v – 1/u = 1/f

• Sign conventions: Distances in the direction of incident light are positive; against are negative.

• For convex lens: f is positive; for concave lens: f is negative.

• Applications: Designing spectacles, cameras, microscopes, and telescopes.

• Magnification: m = v/u = h’/h.

Question 8: Explain the concept of refractive index and its relation with the speed of light.

Answer:

• Refractive index: n = c/v

• It is the ratio of the speed of light in vacuum to the speed of light in the medium.

• Higher refractive index means light travels slower in the medium.

• It determines the amount of bending of light.

• Applications: Designing lenses, prisms, and optical fibres.

Question 9: Explain the power of a lens and its combination with examples.

Answer:

• Power of a lens: P = 1/f (in metres), unit is Dioptre (D).

• Convex lens: P is positive; Concave lens: P is negative.

• Combination of lenses in contact: P = P₁ + P₂ + P₃ + …

• Example: If P₁ = +5 D and P₂ = -3 D, then P = +2 D.

• Applications: Designing optical instruments and corrective lenses.

Question 10: Explain the difference between a convex lens and a concave lens.

Answer:

• Convex lens: Thicker in the middle, converges light, f is positive.

• Concave lens: Thinner in the middle, diverges light, f is negative.

• Convex lens: Can form real and virtual images; Concave lens: Always forms virtual images.

• Convex lens: Used in magnifying glasses, cameras; Concave lens: Used in spectacles for myopia.

• Convex lens: Converging lens; Concave lens: Diverging lens.

Question 11: Explain the formation of a rainbow using the concepts of reflection and refraction.

Answer:

• A rainbow is formed by the dispersion of sunlight by water droplets.

• Sunlight enters a droplet, is refracted, dispersed, and internally reflected, then refracted again.

• This produces a spectrum of colours in the form of a rainbow.

• The red colour appears on the outer edge, and violet on the inner edge.

• A rainbow is always formed in the direction opposite to the Sun.

Question 12: Explain the concept of total internal reflection and its applications.

Answer:

• Total internal reflection occurs when light travels from a denser to a rarer medium.

• The angle of incidence must be greater than the critical angle.

• Applications:

  • Optical fibres: Used in communication and medical endoscopy.

  • Prisms: Used in binoculars and periscopes.

  • Diamonds: Sparkle due to total internal reflection.

  • Mirages: Formed due to total internal reflection in the atmosphere.

📝 How to Use These PYQs for CBSE Exam Preparation

At Dhingra Classes Nashik, we recommend the following strategies to maximize your score using these PYQs.

🎯 Study Tips

1. 📖 Read each question and try to answer before looking at the solution

2. ✏️ Practice writing answers within time limits (1 mark = 1 min, 3 marks = 5 min, 5 marks = 10 min)

3. 🗣️ Focus on repeated themes like mirror formula, lens formula, and refractive index

4. 📝 Create flashcards for 1-mark questions

5. 🔦 Practice ray diagrams for mirrors and lenses

6. 🔄 Revise weekly to ensure long-term retention

7. 📋 Practice numericals using mirror and lens formulas

8. ✅ Take mock tests using these PYQs

🏫 How Dhingra Classes Nashik Helps Class 10 CBSE Students Master Science

At Dhingra Classes Nashik, we provide comprehensive coaching for Science and all other subjects for Class 10 CBSE students. Our approach includes:

• 📚 Structured Lessons: Teaching concepts with clear explanations

• 🔦 Ray Diagram Practice: Regular practice with ray diagrams

• 📝 PYQ Analysis: Regular practice with previous year questions

• ✏️ Regular Tests: Weekly tests to ensure continuous revision

• 🎯 Doubt Clearing Sessions: Personalized attention to every student

• 📊 Progress Tracking: Regular updates to parents about student progress

• 🏆 Numerical Practice: Teaching how to solve problems effectively

📞 Contact Dhingra Classes Nashik

• 📱 Phone: 98230 62106

• 📧 Email: dhingraclassesnsk@gmail.com

• 🌐 Website: www.dhingraclassesnashik.com

• 📍 Address: Plot No 3, XQ3G+H3M Deacon Homes, 301C, opp. Metro Zone, near Guru Govind Sing, Samarth Nagar, Dnyaneshwar Nagar, Pathardi Phata, Nashik, Maharashtra 422009

🏁 Conclusion

Mastering Light: Reflection and Refraction PYQs is essential for Class 10 CBSE students to score high marks in Science board examinations. This comprehensive collection of 1-mark, 2-mark, 3-mark, and 5-mark questions covers all major themes including Reflection of Light, Laws of Reflection, Plane Mirrors, Spherical Mirrors, Concave Mirrors, Convex Mirrors, Mirror Formula, Magnification, Refraction of Light, Laws of Refraction, Snell’s Law, Refractive Index, Lens Formula, Power of Lens, and Combination of Lenses.

By regularly practicing these Previous Year Questions and using them in your board exam preparation, you can improve your understanding and score better. At Dhingra Classes Nashik, we are committed to helping Class 10 CBSE students excel in Science and achieve academic success. Remember, Light: Reflection and Refraction is not just about memorizing formulas—it is about understanding how light behaves and how we can use it to improve our lives.