light : light SECONDARY 3 PHYSICS
What is Light? : What is Light? Light is the part of the EM spectrum which we can see.
Light travels in straight lines called rays.
A bundle of rays is known as a beam of light. A ray A divergent beam A convergent beam
Luminous and Non-Luminous : Luminous and Non-Luminous Luminous objects are those that give off light on its own.
Example: Light bulb, Sun
Non-luminous objects are objects that do not give off light on its own.
Example: table, board, Moon
Reflection : Reflection Reflection is the bouncing of light rays off a surface.
We are able to see non-luminous objects as light is reflected off them.
Reflection : Reflection
Laws of Reflection : Laws of Reflection The incident ray, the reflected ray and the normal all lie on the same plane.
The angle of incidence is equal to the angle of reflection.
Reflection for Different Surfaces : Reflection for Different Surfaces Regular reflection
On smooth surfaces Diffused reflection
On rough surfaces
Properties of Image Formed by Plane Mirror : Properties of Image Formed by Plane Mirror Same size as the object
Laterally inverted (left-to-right inversion)
Upright
Virtual (image cannot be caught on a screen)
Object distance is equal to image distance
Ray Diagram for Reflection : Ray Diagram for Reflection Object, O observer
Slide 10 : Ray Diagram for Reflection Image, I observer Object, O
Ray Diagram (Extended object) : Ray Diagram (Extended object) observer
Slide 12 :
Refraction : Refraction Refraction is the bending of light when it enters from one transparent medium into another.
It is caused by the different speeds of light in different media.
The greater the optical density of the medium, the slower the speed of light.
Refraction : Refraction
Laws of Refraction : Laws of Refraction The incident ray, the refracted ray and the normal all lie in the same plane.
For two particular media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant. (Snell’s Law)
Refractive Index : Refractive Index When light passes from vacuum (or air) into a given medium (eg. water), the constant ratio of is known as the refractive index, n, for that medium. Angle of incidence Angle of refraction
Speed and Refractive Index : Speed and Refractive Index Speed of light in vacuum = 3 x 108 ms-1
Light is found to move slower in optically denser mediums. (eg. glass and water)
Daily Phenomena of Refraction : Daily Phenomena of Refraction Swimming pool and ponds appear shallower than it really is.
Object is at a deeper depth than where it appears to be.
Bent objects in liquids
Total Internal Reflection : Total Internal Reflection Light ray is unable to exit a medium.
Occurs when
Ray of light passes from a denser to a less dense medium
Angle of incidence in the denser medium is greater than the critical angle.
http://www.lightlink.com/sergey/java/java/totintrefl/index.html
Critical Angle : Critical Angle The angle of incidence in the optically denser medium for which the angle of refraction in the less dense medium is 90o. Refractive index Critical angle