What is the law of reflection?

The angle of incidence is equal to the angle of reflection and the incident ray, reflected ray and normal lie in the same plane.

What is refraction of light?

Refraction is the bending of light as it passes from one medium to another with different optical densities.

What is the mirror formula?

Mirror formula relates object distance, image distance and focal length: 1/f = 1/v + 1/u.

5. How to draw a ray diagram for a plane mirror (simple steps)?

Draw two rays from a point on the object: (a) one incident ray parallel to mirror, reflect back at same angle; (b) one incident ray at angle to normal. Extend reflected rays backward to meet — intersection is virtual image point.

9. What are properties of image formed by a convex mirror?

Convex mirror always forms virtual, erect, diminished images located behind the mirror. Focal length is considered negative for convex mirror in sign convention.

18. What are properties of image formed by a concave (diverging) lens?

Concave lens always produces a virtual, erect, diminished image located on the same side as the object. Used in spectacles for myopia (short-sightedness) correction.

19. How is magnification for lenses defined and calculated?

Magnificationm = h'/h = -v/ufor lenses (h' image height, h object height). Sign indicates inversion (negative for inverted image).

21. How do you find equivalent focal length and power for two thin lenses in contact?

For lenses in contact:1/f = 1/f1 + 1/f2. Powers add:P = P1 + P2(P in dioptres).

22. What is dispersion of light by a prism and why does it occur?

Dispersion: splitting of white light into constituent colours due to wavelength-dependent refractive index — shorter wavelengths (violet) refract more than longer (red).

28. For a prism, what is minimum deviation and formula relating refractive index with angle A and Dmin?

Minimum deviation occurs when the path inside prism is symmetrical.n = sin((A + D_min)/2) / sin(A/2), where A is prism angle and D_min is minimum deviation.

30. Why does a coin at bottom of a bowl of water appear nearer to the surface when viewed from above?

Light from coin refracts at water-air surface towards observer, bending away from normal — rays enter eye as if coming from a point closer to surface (apparent depth less than real depth).

31. Why does the Sun appear slightly flattened near the horizon?

Atmospheric refraction: rays from lower limb of Sun bend more (denser air near surface) than upper limb, making the Sun appear flattened vertically. Scattering reddens colour too.

32. How does atmospheric refraction affect observations of stars and planets?

Atmospheric refraction shifts apparent positions of celestial objects upward (near horizon effect is largest), causing stars to be visible slightly before rising and after setting.

33. Why are there primary and secondary rainbows and why is the secondary fainter and reversed?

Primary rainbow: light refracts, internally reflects once, then refracts out. Secondary: two internal reflections — so emerges at larger angles, undergoes more loss (fainter) and colour order is reversed.

34. How are myopia and hypermetropia corrected using lenses?

Myopia (short-sighted): use concave (diverging) lenses to move image onto retina. Hypermetropia (long-sighted): use convex (converging) lenses to form image on retina.

35. Why is some light reflected at a boundary even when not at the critical angle?

At any boundary between different refractive indices, part of light is reflected and part refracted. Reflectance depends on refractive index contrast and angle (Fresnel equations) — qualitatively larger contrast → more reflection.

38. How does a simple camera form an image?

Lenses focus light to form a real inverted image on the film/sensor. Aperture controls light amount and depth of field; focusing adjusts lens-sensor distance to get sharp image.

39. What is accommodation of the eye?

Accommodation: change in focal length of eye's lens by ciliary muscles — lens becomes thicker for near vision and thinner for distant vision to focus images on retina.

40. Why do mirages occur above heated roads?

Mirages are due to refraction in air layers with varying density (temperature gradient). Light bends and may undergo total internal reflection within hot layers, producing illusion of water/reflected sky.

41. How can you determine focal length of a concave mirror practically?

Point mirror at a distant object (sun or far building) so object is effectively at infinity. Measure distance from mirror pole to sharp image on screen — this ≈ focal length.

Class 10 Science — Chapter 10: Light — Reflection & Refraction

By RAAM SETU | NEET, SSC, Railway & Police Bharti Focused Notes 📘

📘 Introduction

In this chapter, you will master Light — Reflection & Refraction, including laws of reflection, refraction, mirror & lens formulas with solved examples. Essential for NEET, SSC, Railway, and Police Bharti preparation and Class 10 board exams.

🔹 Key Concepts

Reflection: Bouncing back of light from a surface
Laws of Reflection: Angle of incidence = angle of reflection
Refraction: Bending of light across different mediums
Snell's Law: n1 sin i = n2 sin r
Mirror & Lens Formulas: 1/f = 1/v + 1/u, magnification formulas

📊 Chapter Summary Table

Concept	Formula / Law	Use
Reflection	Angle i = Angle r	Predict direction of reflected ray
Refraction	Snell's Law	Calculate bending of light
Mirror Formula	1/f = 1/v + 1/u	Solve image formation problems

🧮 Practice Questions

State the laws of reflection. ➡ Show Answer
The angle of incidence is equal to the angle of reflection; the incident ray, reflected ray and normal lie in the same plane.
Define refraction of light. ➡ Show Answer
Refraction is the bending of light as it passes from one medium to another of different optical density.
Write the mirror formula. ➡ Show Answer
Mirror formula: 1/f = 1/v + 1/u, where f = focal length, v = image distance, u = object distance.

Light — Reflection & Refraction — 50 Q&A

NCERT Class 10. Mobile-first UI — Tap question to expand answer. Diagrams responsive for phones.

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Reflection Refraction Mirrors & Lenses Ray Diagrams

NCERT Class 10 — Light: Reflection & Refraction

📘 Introduction

🔹 Key Concepts

📊 Chapter Summary Table

🧮 Practice Questions

1. What is light? Summarize key properties relevant to this chapter.

2. State the laws of reflection.

3. Differentiate regular and diffuse reflection with examples.

4. List properties of image formed by a plane mirror.

5. How to draw a ray diagram for a plane mirror (simple steps)?

6. Define terms related to spherical mirrors: pole (P), centre of curvature (C), radius of curvature (R), principal axis, focal point (F).

7. State mirror formula and magnification (with sign convention).

8. Describe image formation by a concave mirror for various object positions (beyond C, at C, between C & F, at F, between F & P).

9. What are properties of image formed by a convex mirror?

10. What is refraction? State Snell's law and define refractive index.

11. What are absolute and relative refractive indices? Give typical values for air, water and glass.

12. Explain refraction through a glass slab and lateral displacement.

13. Define critical angle and total internal reflection (TIR). When does TIR occur?

14. How does total internal reflection make optical fibres possible and what are applications?

15. State the formula for refraction at a spherical surface (relation between object distance u, image distance v, refractive indices n1,n2 and radius R).

16. State the thin lens formula and lens-maker's formula.

17. Describe image formation by a convex (converging) lens for various object positions.

18. What are properties of image formed by a concave (diverging) lens?

19. How is magnification for lenses defined and calculated?

20. Define power of a lens and unit.

21. How do you find equivalent focal length and power for two thin lenses in contact?

22. What is dispersion of light by a prism and why does it occur?

23. Explain briefly how a rainbow forms.

24. What is apparent depth? Give relation with real depth.

25. Name two lens aberrations and one way to reduce them.

26. Give two practical devices that use reflection and explain briefly.

27. Differentiate real and virtual images with examples.

28. For a prism, what is minimum deviation and formula relating refractive index with angle A and Dmin?

29. (Worked example) A concave mirror of focal length 15 cm forms an image 10 cm from mirror. Find the object distance and magnification.

30. Why does a coin at bottom of a bowl of water appear nearer to the surface when viewed from above?

31. Why does the Sun appear slightly flattened near the horizon?

32. How does atmospheric refraction affect observations of stars and planets?

33. Why are there primary and secondary rainbows and why is the secondary fainter and reversed?

34. How are myopia and hypermetropia corrected using lenses?

35. Why is some light reflected at a boundary even when not at the critical angle?

36. Explain with a simple diagram how a periscope uses two plane mirrors.

37. How do anti‑reflective coatings on lenses work (qualitative)?

38. How does a simple camera form an image?

39. What is accommodation of the eye?

40. Why do mirages occur above heated roads?

41. How can you determine focal length of a concave mirror practically?

42. Why are prisms used in binoculars?

43. How are spectacle lenses prescribed using dioptres (qualitative)?

44. Why does light travel slower in a medium than in vacuum?

45. Why does ability to accommodate decline with age (presbyopia)?

46. What are limits of ray (geometric) optics?

47. Give two methods to find focal length of a convex lens.

48. What determines magnifying power of a simple telescope (qualitative)?

49. Quick formula sheet (one line each): mirror, lens, Snell, critical angle, magnification, power.

50. One-minute high-yield summary: Reflection & Refraction