1. Understanding Formation of a Rainbow By Tin Wei Heng

2. Contents  Rationale  Colours of a rainbow  Introduction to light dispersion  Refraction and reflection of light in water droplet  Maximum angle at which light should leave droplet to see rainbow  Rainbow as a 3D cone

3. Rationale  Understand the formation of rainbow  Understand how light disperses better  Better understand the reflection and refraction of light

4. Colours of Rainbow  Red  Orange  Yellow  Green  Blue  Indigo  Violet  The colours of the Rainbow are also known as the colours of light when it is dispersed

5. Dispersion of light  Dispersion of light occurs when light passes through from one medium to another  This causes different colours to refract at different angles  This phenomenon splits white light into the colours of a rainbow

6. Refraction and reflection of light in a water droplet  Light is first refracted entering the surface of the raindrop,reflected off the back of the drop, and again refracted as it leaves the drop

7. Angle  The most intense light can only leave the droplet at an angle of 42 degrees to see the rainbow  This is because if the sun is higher than 42 degrees, the rainbow will then be below the horizon and usually cannot be seen  This is because there are not usually sufficient raindrops between the horizon(eye level) and the ground  Exceptions occur when the observer is high above the ground E.g. Ferris wheel, aeroplane

8. Formation of a Rainbow(Complete)  Light first enters the droplet at an angle of 42 degrees or less  It is then refracted when entering the surface of the droplet  The light is then dispersed into different colours(colours of the rainbow)  Light is then reflected off the back of the raindrop and again refracted as it leaves the drop

9. After all this hard work you get……..  TADA!!!!!!

10. Thank You