9 Physical Sciences

Light I

Note

Important Points

Light is a form of electromagnetic (EM) radiation energy that travels in transverse waves or straight lines.

What is light?

Light travels faster than sound at a speed of 300, 000, 000 m/s.

c = 300, 000, 000 m/s.

Speed of Light

Light travels faster than sound.During a thunderstorm, you will notice that lightning strikes first.This is then followed by thunder.

Light travels in straight lines. To demonstrate this property, just close your eyes. Did you realise that you could not see any light?

Properties of Light

There are seven different types of EM waves.

Properties of Light

low frequency

Increasing frequency

high frequencylong wavelength short wavelength

Properties of Light

Each form of light travels at the same speed in a vacuum.

Properties of Light

Artificial sourceNatural source Sources of Light

Smooth surfaces like the calm water allows light to be reflected evenly.

This is known as a specular reflection.

Smooth Surfaces

Rough surfaces like the rippled and paddled water allows light to be reflected unevenly.

This is known as a diffuse reflection.

Rough Surfaces

Objects that emits (or produces) their own light.

Luminous Objects

Objects that reflects light.Do not emit any light.

Non-luminous objects

How do we see things?

Light is emitted from luminous objects.

Light hits an object and bounces off.

Our eyes receives the light and is focused on the retina.

Why can we see things?

Visible light is composed of 7 colours of different wavelengths and frequencies.

Why are objects coloured?

When light hits the banana, all colours except for yellow will be absorbed.

Why are objects coloured?

The colour yellow will be reflected and received by the retina in the eye to be interpreted.

Why are objects coloured?

Objects that allow all light to go through.

Transparent Objects

Objects that allows some light to pass through.

Translucent Objects

Objects that do not allow light to pass through.

Opaque Objects

Transparent• Glass

Translucent• Ice

Opaque• Straw• Cutlery

Example: A Glass of Coke