What is light?

• Light is a type of energy.

• It travels in waves.

• It moves very fast, about 300,000 kilometers per second in space.

• Light does not need air or anything to move. It can travel in space.

Types of light (called the electromagnetic spectrum)

There are many kinds of light, but we can only see a small part of it.

From longest wavelength to shortest:

1. Radio waves – used for radios and TVs

2. Microwaves – used in ovens and phones

3. Infrared – felt as heat

4. Visible light – the part we can see

5. Ultraviolet – comes from the sun, can burn skin

6. X-rays – used to see bones

7. Gamma rays – very strong, come from space and nuclear things

Visible light

• This is the light we can see with our eyes.

• It has different colors: red, orange, yellow, green, blue, indigo, violet.

• Red has the longest wavelength, violet has the shortest.

What light can do

• Reflect: bounce off a surface like a mirror

• Refract: bend when it passes through something like glass or water

• Absorb: get taken in by objects (black objects absorb more)

• Transmit: pass through things like clear glass

• Scatter: spread in different directions (why the sky looks blue)

Sources of light

Natural sources:

• Sun

• Stars

• Fire

• Lightning

Artificial sources:

• Bulbs

• Flashlights

• LEDs

• Lasers

How we see

• We see things because light reflects off them and enters our eyes.

• Without light, we cannot see anything.

Properties of light

• Travels in straight lines

• Can be bent or focused using lenses

• Can be split into different colors using a prism

• Can be filtered (polarized)

Wave and particle

• Light behaves like both a wave and a particle.

• The tiny particles of light are called photons.

• This is part of a science called quantum physics.

Uses of light

• Helps us see

• Helps plants grow through photosynthesis

• Used in solar panels to make electricity

• Used in communication (fiber optic cables)

• Used in medicine (lasers, X-rays)

• Used in technology (TVs, cameras, scanners)

my note

I learned that light is the reason we can see everything and it is the reason plants are alive and it is the fastest type of energy in the universe.