the study of the behaviour of light Optics the study of the behaviour of light ½ page Mind map…

This generates shadows. Light is often described in terms of rays that travel in straight lines. This generates shadows. A Bust of Mr Shilloete.

Many rays fan out from a light source but each ray travels in a straight line.

Surveyors use the “straight line” nature of light with lasers.

Light travels through a vacuum.

Light travels at 300 000 000 ms-1. This speed is a significant “constant” and is given its own special symbol - c.

Journey to the moon This diagram shows how long light, rocket, supersonic jet or a runner to reach the moon.

glass silver Mirrors are backed by a very thin layer of metal which reflects the light. paint

Mirrors produce an upright, virtual image that is laterally inverted Lateral Inversion Virtual Cannot be projected onto a screen.

mirror clock mirror clock The clockface faces the mirror. NCEA 90768 2005 mirror The clockface faces the mirror. Sketch the image of the clockface in the mirror. clock mirror 12 6 clock

mirror clock mirror clock The clockface faces the mirror. NCEA 90768 2005 mirror The clockface faces the mirror. Sketch the image of the clockface in the mirror. clock mirror 12 6 clock

i = r Law of reflection i = incident angle r = reflected angle measured from the normal r = reflected angle A line  to the surface at the point of incidence i = r Law of reflection

Angle of incidence Angle of reflection = i = r

Image in a Plane Mirror Mirror Object Image Plane mirror activity

NCEA 90768 2005 Copy the diagram accurately and draw in the paths of the reflected light rays, hence show the position of the image and the lines to show how the image was formed. // normal ACCURACY TO ± 1O

ACCURACY TO ± 1OIncident and final reflected ray must be parallel. Two plane (flat) mirrors are fixed exactly at right angles (90º) to each other, as shown in the diagram below. A ray of light is aimed at one of the mirrors as shown. Copy this diagram and accurately draw rays to show how this ray reflects. NCEA 90768 2006 ACCURACY TO ± 1OIncident and final reflected ray must be parallel.

Two plane (flat) mirrors are fixed exactly at right angles (90º) to each other, as shown in the diagram below. A ray of light is shown. Explain what would happen to the light rays if the mirrors were placed at an angle greater than 90° to each other. Using diagrams may help you with your answer. NCEA 90768 2006 <135o > 135o As the angle between the mirrors increases (greater than 900) the incident ray and the final ray diverge more and more until the 1st reflected ray misses the second mirror altogether.

Ex: glossy vs. flat paint

The smooth plane mirror is in a room with a rough concrete floor. The light intensity is even over the whole room. Which of the two surfaces will receive the most light? Which of the two surfaces will reflect an image? Explain your answers. The plane mirror The concrete surface

The plane mirror The concrete surface The smooth plane mirror is in a room with a rough concrete floor. The light intensity is even over the whole room. Which of the two surfaces will receive the most light? Which of the two surfaces will reflect an image? a) Both surfaces will receive the same amount of light The plane mirror The reflected light is not scattered in the mirror so a virtual image is formed. The reflected light is scattered by the concrete so an image is not formed The concrete surface

Multiple Reflections ( 2 or more mirrors) object image image image