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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 can help 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. 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 From air into water or glass • 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 plastic 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 Reflection When 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.