🎯Here are exam-focused notes + topic-wise previous year questions (PYQs) & NCERT exercise solution -
1️⃣ Reflection of Light
- Reflection: Bouncing back of light from a surface.
- Laws of Reflection:
- Angle of incidence = Angle of reflection.
- Incident ray, reflected ray, and normal all lie in the same plane.
2️⃣ Spherical Mirrors
- Concave mirror (converging)
- Convex mirror (diverging)
3️⃣ Image Formation by Concave Mirror
|
Position of Object |
Position of Image |
Nature of Image |
|
At infinity |
At focus (F) |
Point-size, Real, Inverted |
|
Beyond C |
Between C and F |
Real, Inverted, Smaller |
|
At C |
At C |
Real, Inverted, Same size |
|
Between C and F |
Beyond C |
Real, Inverted, Enlarged |
|
At F |
At infinity |
Real, Inverted, Highly enlarged |
|
Between F and P |
Behind mirror |
Virtual, Erect, Enlarged |
4️⃣ Uses of Mirrors:
- Concave mirror: Torches, headlights, shaving mirrors.
- Convex mirror: Rear-view mirrors (wide field of view).
5️⃣ Sign Conventions:
- Distances measured towards mirror (left) → Negative.
- Distances measured away from mirror (right) → Positive.
6️⃣ Mirror Formula:
\frac{1}{f} = \frac{1}{v} + \frac{1}{u}
Where:
f: focal length,
u: object distance,
v: image distance.
🔷 Refraction of Light
- Bending of light when it passes from one medium to another.
- Laws of Refraction:
- Incident ray, refracted ray & normal lie in the same plane.
- Snell’s Law:
n = \frac{\sin i}{\sin r}
where n is refractive index.
7️⃣ Refractive Index:
n = \frac{\text{speed of light in vacuum}}{\text{speed of light in medium}}
8️⃣ Real and Apparent Depth:
- Pool appears shallower due to refraction.
9️⃣ Lenses (brief overview if covered in your exam)
- Convex lens: Converging
- Concave lens: Diverging
- Similar formulas and conventions as mirrors.
📄 Previous Year Questions (PYQs)
🌟 Very Short Answer (1–2 Marks)
✅ State the laws of reflection.
✅State the laws of reflection of light.
✅Why is a convex mirror used as a rear-view mirror?
✅Draw a ray diagram for image formation when object is placed beyond C for a concave mirror.
✅Define principal focus and radius of curvature.
✅State and explain Snell’s Law.
✅ Define the principal focus of a concave mirror.
✅ Give one use each of convex and concave mirrors.
✅Define refractive index.
✅Why does a pencil appear bent in water?
✅Light enters from air to glass; how does its speed change?
✅ What is meant by the power of a lens?
✅ What happens to a ray of light when it passes from air to glass?
✅ Draw a labeled ray diagram for concave mirror when object is at F. (2 Marks)
✅ Show bending of light as it passes from air to water and mark angles. (2 Marks)
🌟 Short Answer (3 Marks)
✅ Draw a ray diagram to show the image of an object placed between F and 2F in a convex lens.
Derive the mirror formula.
✅ Derive the relationship between real and apparent depth.
✅ Write mirror formula & explain the terms.
✅ Why is a convex mirror used as a rear-view mirror?
✅ Write the relation between refractive index & speed of light in a medium.
✅ What is magnification? Write its formula.
✅ An object is placed at 20 cm from a concave mirror of focal length 15 cm. Find the position and nature of the image. (3 Marks)
✅ A ray of light passes from glass (n = 1.5) to air. If angle of incidence is 30°, calculate the angle of refraction. (3 Marks)
🌟 Long Answer (5 Marks)
✅ Derive the mirror formula.
✅ Derive the lens formula.
✅ With ray diagrams, explain image formation by concave mirror for different positions of the object.
✅ Draw a neat labelled diagram to show refraction through a glass slab & explain lateral displacement.
🔔 Tips for Exams:
✨ Always label diagrams properly.
✨ Use the sign convention carefully.
✨ Memorize standard ray diagrams.
✨ Write laws and definitions clearly.
✨Practice all ray diagrams (mirrors & lenses).
✨Learn the formulas: mirror, lens & magnification.
✨Memorize uses of different mirrors & lenses.
✨Remember sign conventions.
✨Solve numerical problems based on formulae.
📋 Suggested Diagrams to Prepare:
🔷Image formation by concave & convex mirrors.🔷Image formation by concave & convex lenses.
🔷Refraction of light through glass slab.
🔷Lateral shift diagram.