# SP5 All notes

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• Created by: IzzyB1
• Created on: 11-06-18 19:41

Ray diagrams

They are a way of showing what happens when light is relected or refracted.

Normal - line drawn at a right angle to the boundary

The incident ray and reflected ray are always measured from the normal.

Law of reflection

1. angle of reflection = angle of incidence

2. the incident ray, reflected ray and normal ray all lie on the same plane

Refraction

Light travels at different speeds in different materials. It travels faster in air than in water or glass. It changes direction when it changes speed. This is called refraction.

The angle of incidence and angle of refraction are both measured from the normal. When light meets a boundary at right angles to it, there's no change in direction.

Total Internal Reflection

When light passes from water or glass into air with small angles of incidence, most of the light passes through the boundary, but a little is reflected. As the angle of incidence increases, the angle of refraction also increases until the refracted light passes along the boundary. If the angle if incidence increases further, the light is completely reflected in the glass. This is called total internal reflection. The angle of incidence in which this starts to happen is the critical angle.

Colour

Luminous objects - visible as light from them enters our eyes

Non-luminous objects - visible because they reflect light

Diffuse reflection - when rough surfaces scatter reflected light