Reflection D. Crowley, 2008

Reflection To know what reflection is, and the law of reflection

Speed Of Light Using the information given in the diagram, work out: -  The distance between the Earth and the Sun  The distance between the Earth and the Moon Earth Moon Sun Speed of light = 300’000 km/sec Time taken for light from Sun to reach Earth = 510 seconds Time taken for reflected light from Moon to reach Earth = 1.3 seconds Speed Distance Time

Sun & Earth Light from Sun takes 510 seconds to reach Earth Distance = Speed x Time Distance = 300’000 x 510 Distance between Sun and Earth = 153’000’000 km Earth Moon Sun Speed Distance Time

Moon & Earth Reflected light from Moon takes 1.3 seconds to reach Earth Distance = Speed x Time Distance = 300’000 x 1.3 Distance between Moon and Earth = 390’000 km Earth Moon Sun Speed Distance Time

Reflection Light is able to bounce of surfaces - this is known as reflection There are two types of reflection: clear & diffuse  Light can reflect off an even surface (such as a smooth and shiny mirror) where all the light is reflected off at the same angle - this is a clear reflection  Light can also reflect off uneven surfaces (such as a piece of paper) at lots of different angles - this is diffuse reflection Clear reflection Diffuse reflection

Reflection  Mirrors are very smooth and shiny - they reflect light evenly and we can see an image in them  Bumpy or rough surfaces do not reflect light evenly - instead, light is scattered in all directions, and usually we cannot see an image Mirrors reflect light evenly, but rough surfaces scatter light

Reflection Of Plane Mirrors The angle of incidence = the angle of reflection A line at 90 o to the surface of a mirror is called the normal A ray of light going to the mirror is the incident ray A ray that comes off the mirror is the reflected ray The angle of incidence is the angle between the incident ray and the normal The angle of reflection is the angle between the reflected ray and the normal

Reflection Of Plane Mirrors The angle of incidence = the angle of reflection For example: - If the angle of incidence was 30 o, the angle of reflection would be 30 o If the angle of incidence was 60 o, the angle of reflection would be 60 o

Investigation  Using the protractors, ray boxes, and mirrors investigate the rules of reflection for plane mirrors  Set up the ray box so the light is reflected off a mirror. Measure both the angle of incidence and the angle of reflection for a variety of situations…

Mirrors  Complete the mirrors worksheet

Mirrors