LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER

1 1 KS3 SCIENCE - PHYSICS KS3 SCIENCE - PHYSICS Light & Optics Light & Optics

LIGHT & DARK 2 2

3 3 Things which give off light can be seen because some of that light reaches the eye Things which give off light can be seen because some of that light reaches the eye

LIGHT & DARK 4 4 Things which do not give off light can be seen because they usually reflect light Things which do not give off light can be seen because they usually reflect light

LIGHT & DARK 5 5 When light cannot pass through an object, it creates a shadow When light cannot pass through an object, it creates a shadow

LIGHT & DARK 6 6 Light travels so quickly it seems to arrive in an instant - the speed of light is 300 million m/s Light travels so quickly it seems to arrive in an instant - the speed of light is 300 million m/s

REFLECTION 7 7

8 8 A mirror image appears the same size as the original object, the right way up A mirror image appears the same size as the original object, the right way up

REFLECTION 9 9 The “Angle of Incidence” of light rays is always the same as the “Angle of Reflection” The “Angle of Incidence” of light rays is always the same as the “Angle of Reflection” “Normal”

REFLECTION 10 So the image appears the same distance from the mirror as the original object So the image appears the same distance from the mirror as the original object

REFLECTION 11 But the image is laterally inverted as the positions of light rays are reversed But the image is laterally inverted as the positions of light rays are reversed

REFLECTION 12 The image is described as “Virtual” because it would not appear on a screen placed behind the mirror The image is described as “Virtual” because it would not appear on a screen placed behind the mirror

REFRACTION 13

Perspex Block Perspex Block REFRACTION 14 Light rays pass through different substances at different speeds, so rays appear to bend first one way and then the other Light rays pass through different substances at different speeds, so rays appear to bend first one way and then the other

Prism REFRACTION 15 White light contains different colours of light, each of which has a different wavelength White light contains different colours of light, each of which has a different wavelength White Light White Light

Prism REFRACTION 16 Moving through a prism the speed is changed, but this affects colours differently leading to “Dispersion” Moving through a prism the speed is changed, but this affects colours differently leading to “Dispersion” White Light White Light

REFRACTION 17 Red, blue and green are called “Primary Colours” - they cannot be made by mixing other colours, but can be used to mix other colours Red, blue and green are called “Primary Colours” - they cannot be made by mixing other colours, but can be used to mix other colours

LENSES 18

LENSES 19 Convex or converging lenses refract light so that the rays are brought together Convex or converging lenses refract light so that the rays are brought together

LENSES 20 A concave or diverging lens refracts light so that rays are separated outwards A concave or diverging lens refracts light so that rays are separated outwards