Physics P8

Light

Angle of incidence = Angle of reflection

Periscope

Position of Image – the image is as far behind the mirror as the object is in front

Lateral inversion

Real and Virtual Images

The image being reflected in the first diagram above is a virtual image. When looking at a mirror image, the light rays that reflect off the mirror into your eye appear to come from the image. This virtual image cannot be projected onto a screen like at the cinema, unlike a real image. A real image can because it is formed by focusing light rays onto a screen.

Refraction

Rules for refraction

• Ray of light bends towards the normal when it slows down

• Ray of light bends away from the normal when it speeds up

• A ray of light travelling along the normal is not refracted

Real and apparent depth

Key terms:mediumnormalintersectincident rayrefracted rayparalleloptical density

Semi-circular block

Visible Light

Prisms

Dispersion

Total Internal Reflection• https://www.cdli.ca/courses/phys2204/unit04

_org02_ilo11/b_activity.html

• This is caused by refraction of rays from an optically dense medium to an optically less dense medium (e.g. glass to air)

Critical Angle

• At the critical angle (cº) the angle of refraction is 90º

• If the angle of incidence is greater than the critical angle, all of the light is reflected inside the denser medium.

• The light shows total internal reflection.

Optical Fibres

Uses of optical fibres

• Communincations • Medecine