# Light

## **Section 1: Light**

### **1. What is Light?**

* Light is a form of **energy** that travels as a **wave**.
* It is part of the **electromagnetic spectrum**.
* Light can travel through a **vacuum** (empty space), unlike sound.

#### Key Fact:

* The speed of light is **300,000,000 m/s (3 × 10⁸ m/s)**.
* This is the **fastest possible speed in the universe**.

***

### **2. Light vs Sound**

* Light travels **much faster** than sound.
* Example: You see lightning before you hear thunder.

***

### **3. How Light Interacts with Materials**

When light hits a material, three things can happen:

#### **a) Absorption**

* Light energy is taken in by the material.
* Often converted into **heat**.

#### **b) Reflection**

* Light bounces off a surface.

There are two types:

* **Specular reflection**
  * Smooth surface (mirror)
  * Clear image formed
* **Diffuse scattering**
  * Rough surface
  * Light is scattered in many directions
  * No clear image

***

### **4. Types of Materials**

#### **Transparent**

* Lets most light pass through
* Clear image seen
* Example: glass

#### **Translucent**

* Lets some light through
* Blurry image
* Example: frosted glass

#### **Opaque**

* Lets no light through
* Example: wood, metal

***

### **5. Refraction (Bending of Light)**

#### Definition:

Refraction is when light **changes direction** as it passes between different materials.

#### Why does it happen?

* Light **changes speed** in different materials.

#### Key Rule:

* Slows down → bends **towards** the normal
* Speeds up → bends **away** from the normal

***

### **6. Lenses and Refraction**

#### Convex Lens (Converging Lens)

* Bends light **inwards**
* Focuses light to a point (focal point)

#### Example:

* The **human eye** uses a convex lens to focus images on the retina.

***

### **7. Dispersion of Light**

#### White Light:

* Made up of all colours of the visible spectrum.

#### When passed through a prism:

* Light splits into colours:
  * Red, Orange, Yellow, Green, Blue, Indigo, Violet

#### This is called **dispersion**.

#### Why does it happen?

* Different colours travel at **different speeds**, so they bend by different amounts.

***

### **8. Colours and Frequency**

* Each colour has a different **frequency**:
  * Red = lowest frequency
  * Violet = highest frequency

***

### **9. Filters and Colour**

#### How coloured objects work:

* They **reflect** their own colour
* They **absorb** all other colours

#### Example:

* A red object:
  * Reflects red light
  * Absorbs all other colours

#### Filters:

* Only allow certain colours through
* Absorb the rest

***

### **Quick Summary**

* Light travels extremely fast and can move through a vacuum.
* It can be absorbed, reflected, or refracted.
* Refraction happens due to speed changes in different materials.
* White light contains all colours and can be split using a prism.
* Objects appear coloured because they reflect certain wavelengths.


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