Chapter 4 (8) Light and Optical Systems

Light behaves in predictable ways

Text book pages 92-95 Do 7.1 – 7.3 in your

workbooks

Light Interaction• Depending on the

situation, light will reflect, absorb and transmit at or through objects.

• Remember that light travels in straight lines from objects to your eyes.

Ray Diagrams• Ray diagrams are used

to show how light travels.

• Light traveling from a source is shown as a straight line called a ray.

• Ray diagrams can help explain why the brightness or intensity of light changes with distance.

• Ray diagrams also help to explain shadows. A lack of light is considered to be a shadow.

Ray Diagrams• Light hits an object and is reflected to the eye thereby producing an image of the object.

Light Interacts With Materials

• When light hits an object, it behaves in different ways depending on they type of the material each object is made of.

• Transparent materials can transmit light – it passes right through them.

• Eg. Glass, clear plasticFrom air into water or glass

Other types of materials that light comes into contact with

• Translucent – allow some, but not all, light to pass through. Eg. Frosted window pane.

• Opaque – do not let any light through. They absorb or reflect the light. Shadows are created as light passes in front of these materials. Eg. Brick, wood, metal.

Other Types of Materials• Non-Luminous – they

do not produce light. Also includes opaque objects.

• Luminous – a light source. Eg. Lamp, the sun, fire.

Types of Reflection: Regular Reflection• Regular Reflection –

light rays hit a smooth surface.

• Light rays are parallel to each other.

• Reflected at same angle.

• Produce clear image.

Types of Reflection:Diffuse Reflection• Diffuse Reflection – when

light rays strike a rough or uneven surface.

• Reflected at a different angle.

• Rays do not remain parallel.

• Scatter the light rays.

• Can see objects from many positions.

The Law of Reflection• Incident Rays – are the incoming rays of light.

• The shinier and smoother the surface the better the reflection.

• Plane Mirrors – flat mirrors – will allow for the clearest of reflections

The Law of ReflectionWhen a ray of light hits a plane mirror at an angle, it

bounces off the mirror surface at exactly the same angle.

The “Normal” – a line perpendicular to the mirror at the point of reflection

Angle of incidence – the angle between the incident ray and the normal

Angle of reflection – the angle between the reflected ray and the normal.

The Law of Reflection cont…• THE LAW OF

REFLECTION – the angle of incidence is equal to the angle of reflection.