CBSE Class 10 Science Chapter 9 Light – Reflection and Refraction

Light – Reflection and Refraction is a chapter in your science subject. Radhe Radhe to all my dear children! You all will have to work very hard for your board exams to get good marks. In this post, I will try to cover all the important topics of your 10th-grade science syllabus so that you can understand and remember them.

Light – Reflection and Refraction , which is your ninth chapter, falls under the physics section of science. All the information you need to study in this chapter will be found in this post.

Also Read- CBSE Class 10 Science Chapter 4 Carbon and Its Compounds

Key Content of Chapter 9 Light – Reflection and Refraction

1️⃣ What is Light?

• Light is a form of energy that enables us to see objects.
• We see objects when light falls on them and gets reflected into our eyes.
• Light generally travels in straight lines, called rays of light.

2️⃣ Reflection of Light

🔹 Reflection

Reflection is the bouncing back of light when it strikes a polished surface like a mirror.

🔹 Laws of Reflection

1. Angle of incidence = Angle of reflection
2. Incident ray, reflected ray and normal lie in the same plane

3️⃣ Plane Mirror – Image Characteristics

• Image is virtual and erect
• Image size = object size
• Image distance = object distance
• Image is laterally inverted

4️⃣ Spherical Mirrors

🔹 Types

1. Concave Mirror – reflecting surface curves inward
2. Convex Mirror – reflecting surface curves outward

🔹 Important Terms (Spherical Mirrors)

• Pole (P): Centre of mirror
• Centre of Curvature (C): Centre of sphere of which mirror is a part
• Radius of Curvature (R): Distance between P and C
• Principal Axis: Line joining P and C
• Principal Focus (F):
  • Concave: Rays parallel to axis meet at F
  • Convex: Rays appear to come from F
• Focal Length (f): Distance PF
  👉 R = 2f

5️⃣ Image Formation by Concave Mirror (Summary)

6️⃣ Uses of Concave Mirror

• Torch, headlights
• Shaving mirror
• Dentist mirror
• Solar furnace

7️⃣ Image Formation by Convex Mirror

8️⃣ Uses of Convex Mirror

• Rear-view mirror in vehicles
  ✔ Wide field of view
  ✔ Always erect image

9️⃣ Mirror Formula & Magnification

🔹 Mirror Formula

$$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$$v1​+u1​=f1​

🔹 Magnification

$$m=\frac{h^{\mathrm{\prime }}}{h}=-\frac{v}{u}$$m=hh′​=−uv​

• m +ve → virtual image
• m –ve → real image

🔟 Refraction of Light

🔹 Refraction

Bending of light when it travels from one transparent medium to another due to change in speed.

🔹 Examples

• Pencil appears bent in water
• Coin appears raised in water
• Letters appear raised under glass slab

1️⃣1️⃣ Laws of Refraction (Snell’s Laws)

1. Incident ray, refracted ray and normal lie in same plane
2. $$$$

\frac{\sin i}{\sin r} = constant
]

1️⃣2️⃣ Refractive Index (n)

$$n=\frac{\text{Speed of light in air}}{\text{Speed of light in medium}}$$n=Speed of light in mediumSpeed of light in air​

• Higher n → optically denser medium
• Light bends towards normal (rarer → denser)
• Light bends away from normal (denser → rarer)

1️⃣3️⃣ Refraction through Glass Slab

• Emergent ray is parallel to incident ray
• Light undergoes lateral displacement

1️⃣4️⃣ Lenses

🔹 Types

1. Convex Lens – converging, thick in middle
2. Concave Lens – diverging, thin in middle

🔹 Important Terms (Lenses)

• Optical centre (O)
• Principal axis
• Principal focus (F₁, F₂)
• Focal length (f)

1️⃣5️⃣ Image Formation by Convex Lens (Key Points)

• Can form real or virtual images
• Used in magnifying glass, camera, microscope

1️⃣6️⃣ Image Formation by Concave Lens

• Image is always virtual, erect and diminished
• Used in spectacles (myopia)

1️⃣7️⃣ Lens Formula

$$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$$v1​−u1​=f1​

🔹 Magnification (Lens)

$$m=\frac{h^{\mathrm{\prime }}}{h}=\frac{v}{u}$$m=hh′​=uv​

1️⃣8️⃣ Power of a Lens

$$P=\frac{1}{f}$$P=f1​

• Unit: Dioptre (D)
• Convex lens → +ve power
• Concave lens → –ve power

Also Read- CBSE Class 10 Science Chapter 4 Carbon and Its Compounds

Class 10 Science Chapter 9 Light – Reflection and Refraction Notes

Science Chapter 9 Light – Reflection and Refraction MCQs

Also Read- CBSE Class 10 Science Chapter 6 Control and Coordination

FAQs About Light – Reflection and Refraction