Lenses © D Hoult 2008

When light goes through glass (or any other transparent substance), its speed changes

When light goes through glass (or any other transparent) substance, its speed changes This can cause it to change its direction of motion

When light goes through glass (or any other transparent) substance, its speed changes This can cause it to change its direction of motion The change in direction is called refraction of light

image

real image

By calculation

By calculation 1 1 1 = + f u v

By calculation 1 1 1 = + f u v 1 = v

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 3 cm

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 3 cm u = 5 cm

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 3 cm u = 5 cm 1 1 1 _ = v 3 5

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 3 cm u = 5 cm _ 1 1 1 5 3 _ = = v 3 5 15

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 3 cm u = 5 cm _ 1 1 1 5 3 _ = = v 3 5 15 Therefore v =

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 3 cm u = 5 cm _ 1 1 1 5 3 _ = = v 3 5 15 Therefore v = 7.5 cm

image

virtual image

By calculation

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 5 cm u = 3 cm

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 5 cm u = 3 cm 1 1 1 _ = v 5 3

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 5 cm u = 3 cm _ 1 1 1 3 5 _ = = v 5 3 15 Therefore v =

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 5 cm u = 3 cm _ 1 1 1 3 5 _ = = v 5 3 15 Therefore v = - 7.5 cm

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 5 cm u = 3 cm _ 1 1 1 3 5 _ = = v 5 3 15 Therefore v = - 7.5 cm the negative tells us

By calculation 1 1 1 = + f u v 1 1 1 _ = v f u f = 5 cm u = 3 cm _ 1 1 1 3 5 _ = = v 5 3 15 Therefore v = - 7.5 cm the negative tells us that the image is virtual