2. Refraction Refraction happens when light moves from one medium to another (example: from air to glass) Wave slows down Bends towards the normal line Wavelength decreases Wave speeds up Bends away from the normal line Wavelength increases IN  TOWARDS OUT  AWAY

3. Dispersion Different colours have different wave speeds through prism They have a different refractive index So they refract by different amounts Red refracts least, red refracts most (Violet is the biggest bender)

4. Three Refraction formulae (IT’S JUST PUTTING IN THE NUMBERS) 1 REFRACTIVE INDEX – How much the speed changes Refractive index, n= Speed in light in a vacuum Speed of light in medium 2 SNELL’S LAW – How to calculate the refractive index Angle of incidence, i Angle of refraction n = Sin i Sin r

5. 3 The critical angle & Total internal reflection) More dense fibres Less dense fibres TIR only happens when light travels from a more dense material to a less dense material & the angle is greater than the critical angle Sin c = n r nini c = the critical angle n r = index of material light has entered n I = index of material light has come from

6. Convex lenses (converging lenses) Parallel rays are brought together Diverging rays are made parallel The thicker the lens the more the rays are bent

7. Uses 1.Magnifying glass & projectors– to make images larger 2. Camera – to focus the image on the film / sensor When magnifying: Magnification = image size object size Lenses are moved forwards and backwards to focus an image

8. Finding the position & size of an image Object Image is where they meet Focal point 1. Draw a line from the top of the object through the middle of the lens 2 Draw a line across to the centre of the lens 3 Draw a line from the centre through the focal point

9. e.g. Cameras e.g. Magnifying lens e.g.Projectors