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Light and Colours. Done by: Soon Wei Jun (23) 2P4. Properties of Light . Travels in straight line Form of energy When it hits an object, it can either be reflected or refracted. Travels at a super fast speed in vacuum. When does Light get reflected/refracted??. Reflection:

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Light and colours

Light and Colours

Done by: Soon Wei Jun (23)


Properties of light
Properties of Light

  • Travels in straight line

  • Form of energy

  • When it hits an object, it can either be reflected or refracted.

  • Travels at a super fast speed in vacuum

When does light get reflected refracted
When does Light get reflected/refracted??

  • Reflection:

    Light is reflected when it hits an opaque object

  • Refraction:

    Light is refracted when it enters a transparent medium of different density…

Reflection of light
Reflection of Light

  • Is when light bounced off an opaque object

  • Allows us to see objects in our surroundings

  • Two types of ray:

    1.Incident ray – light ray coming towards surface

    2.Reflected ray – light ray bouncing off the surface

Rays and beams
Rays and beams

  • Ray of light is indicated by a straight line

  • Beam of light are collective light rays

  • Different beams

    1.Divergent beam

    2.Convergent beam

    3.Parallel beam

Type of reflections
Type of reflections

  • Regular reflection

    -Takes place when light rays are incident on smooth surface; so they are reflected in a regular manner

  • Diffused reflection

    -Takes place when light rays are incident to rough surface; so are reflected in diffused manner

Two laws of reflection
Two laws of reflection

  • 1st: Angle of the incidence must always be equivalent to the angle of reflection

  • 2nd: Incident ray, reflected ray and normal ray must lie in same plane in a reflection diagram

Examples when reflection takes place
Examples when reflection takes place

  • Mirrors!!

    - Do you know that there are different kinds of mirrors, where each of them have different uses/purposes!!


  • Plane Mirror

    -Decorative purposes to make the room appear bigger

    -As a rear mirror to see traffic behind a vehicle

    -As periscope where the user can see any object around the corner


  • Convex mirror

    -Allows us to see things around a bend

    -As a side window to have a wider field of vision to drivers

    -Surveillance purposes: For wider view to observe people in a room to spot shoplifters


  • Concave mirror

    -Dental: magnify the teeth image

    -In a microscope to magnify microorganisms

    -Cosmetic mirrors whereby it can help by magnifying face image


  • Now, let’s move on refraction!

  • So what is a refraction???

    -It is actually the bending of light rays when they travel from one transparent medium to another transparent medium..

    -Only possible with the change in speed of the light rays

When can it take place
When can it take place?

  • Transparent media like






Different speeds of light
Different speeds of light

  • Light travels at different speed in different media

  • It can move faster in less dense medium

  • But in a denser medium, the speed of light is slowed down

Measurement of refraction of light
Measurement of refraction of light

  • Measure through refractive index

  • Equation:

    n(reflective index) = sin incident/sin reflaction

In some special cases
In some special cases…

  • No refraction in conditions like:

    1.Light travelling perpendicular to boundary of media, even if have different densities

    2. Light passes through two media of the exact same densities

Effect it has
Effect it has

  • Due to refraction, object under water appears to be nearer to the surface than it really is

  • Simple example:

    Place a straw in a cup of water and look at the straw by the sight of the cup.. What do you see?

    This is the phenomena which we call refraction!

Now moving on the colours
Now, moving on the colours

  • Dispersion of white light:

    -Composed of seven colour components

    -Each one refracts at different angel

    -So white light will be dispersed by prism and displays a spectrum of seven colour components

    Amazing right?

Primary colours
Primary colours

  • White light can be produced by mixing three distinct colour components(primary colours)

  • Red + Blue + Green = White

  • These primary colours are colours that cannot be reproduced by mixing other colours

Secondary colours
Secondary colours

  • Secondary colours can be produced by mixing two of these primary colours together..

Seeing coloured objects
Seeing coloured objects

  • Colour of an object depends on the colour of light being reflected to the observer

  • Object appears black if absorbs all colour components of white light

  • Object appears white if reflects all colour components of white light

Coloured filter
Coloured filter

  • This is actually a type of plastic or glass that allows only its own colour component of light to pass through

  • So when yellow light passes through a cyan filter, it appears green

  • What is even more cool is that when no light passes through it, the filter appears black!!

End of presentation
End of presentation

  • Thank You!!! 