Light energy is a form of energy that enables us to see objects.

It is a type of electromagnetic energy that travels in straight lines called rays.

Light is produced by sources such as the Sun, electric bulbs, and flames.

(a) Natural Sources

1. Sun – main source of natural light and heat


2. Stars – produce light visible at night


3. Fire – e.g., candle flame, torch

(b) Artificial Sources

1. Electric bulb – converts electrical energy to light


2. Fluorescent tube – bright light source in classrooms and offices


3. LED lights – energy-efficient light sources


4. Torchlight – portable light powered by batteries

1. Light travels in straight lines – can be demonstrated using a pinhole or laser pointer


2. Light is visible – enables objects to be seen


3. Light can be reflected – bounces off smooth surfaces like mirrors


4. Light can be refracted – bends when passing from one medium to another, e.g., air to water


5. Light can be absorbed – dark surfaces absorb more light and heat


6. Light travels faster than sound – speed of light in air is approximately 3 × 10⁸ m/s

Reflection is the bouncing back of light from a surface.

Types of Reflection

1. Regular (specular) reflection – occurs on smooth surfaces like mirrors, producing clear images


2. Diffuse reflection – occurs on rough surfaces, scattering light in many directions

Laws of Reflection

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


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

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

Examples: straw appearing bent in water, lenses focusing light

Refraction is responsible for magnifying effects of lenses and the formation of rainbows

Vision occurs when light enters the eyes from objects and forms images on the retina.

The eye works like a camera, focusing light with the lens.

Proper vision depends on the cornea, lens, and retina working together.

Dispersion is the splitting of white light into its constituent colours when it passes through a prism or water droplets.

A rainbow is formed by dispersion, refraction, and reflection of sunlight in raindrops.

Colours of the rainbow: Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV)

(a) Shadows

A shadow is formed when an opaque object blocks the path of light.

Parts of a shadow: umbra (full shadow) and penumbra (partial shadow)

(b) Eclipses

1. Solar eclipse – occurs when the Moon blocks sunlight from reaching Earth


2. Lunar eclipse – occurs when Earth blocks sunlight from reaching the Moon

1. Enables vision


2. Used in communication (fiber optics, signaling)


3. Used in photography and projectors


4. Used in solar energy to generate electricity


5. Used in medical applications (laser treatment, X-rays)

1. Minimize wastage of artificial light by turning off unused lights


2. Use reflectors and light-colored walls to spread light efficiently


3. Use energy-efficient bulbs like LED and fluorescent tubes

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CONCLUSION

1. Light energy is essential for seeing, communication, energy generation, and medical purposes


2. Understanding the properties, reflection, refraction, vision, dispersion, and formation of rainbows helps us use light efficiently in everyday life