9 ps light i ao
TRANSCRIPT
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