Transcript Refraction
REFRACTION What is Refraction? Refraction is the bending of light rays as they travel from one medium to another. Medium – a material that is part of a process. The cause of refraction is the changing in the speed of light as it travels through the various media. For example, the speed of light slows down as you go from air to water. Refraction The light from the spoon is bent at the surface of the water. This makes the spoon appear broken. The Speed of Light Light can travel at a speed of 300,000 km/s in a vacuum – a space with little or no particles in it. This means that light travels 300million metres every second! (300,000,000 m/s) As more particles get in the way, it gets harder for light to get from one place to another. The particles slow down the passage of the waves that make up the light. The Index of Refraction The index of refraction is a list that gives you an idea of how easily light waves can travel through a medium. The higher the number, the harder it is for light to travel through the medium. A vacuum is 1.0 – the easiest for light to travel through. Air is 1.003 and water is 1.33. To calculate the index of refraction for a material: Index of refraction = speed of light in vacuum speed of light in medium n=c v How Light Refracts A light beam contains several rays – all traveling parallel at the same speed. It strikes the surface of the new medium and “bends” because the particles of the new medium interfere with its movement. The light rays then travel parallel at the same speed, but, in the new direction in which they were bent. How Light Refracts Drawing Refraction Diagrams Draw a line the that is at 90° to the surface where the two media meet – this is the normal. The normal is drawn where the incident beam strikes the second medium. Drawing Refraction Diagrams Now you have to consider the two materials… • If you are going from low refractive index to a higher one – the light bends toward the normal. (Air 1.003 water 1.33) Drawing Refraction Diagrams Again, consider the two materials… • If you are going higher to lower – the light will bend away from the normal. (Water 1.33 Air 1.0003) Refraction Video – Bill Nye!!! THE END