Reflection

To review reflection of lightTo use a ray box safely

To compare regular and irregular reflection

To recall colour in terms of reflection

• Light travels in straight lines•It creates shadows•The further from a light source the less the illumination•It can be reflected from shiny surfaces

Properties of Light?

A plane mirror reflects light regularly so it produces a clear image, which is the same size as the object.The image appears the same distance behind the mirror as the object is in front of it.

When an object is reflected in a plane mirror, left appears as right and right appears as left. This type of reversal is called lateral inversion.

What is lateral inversion?

What is different about the image compared to the object?

1. Fix a plane mirror to a piece of paper and draw around it.

Angle of incidence [i]

Angle of reflection [r]

angle i

angle r

2. Draw a normal (at 90°) through the centre of the mirror outline.

3. Use a ray box to shine an incident ray at the mirror – plot the incident and reflected rays.

4. Measure the angles of incidence [i] and reflection [r] and record the results.

5. Repeat for another four angles of incidence.

6. What do the results show?

Reflection practice

Regular Reflection ray diagram

Irregular reflection

• Regular reflection gives an image in a mirror because the surface of the mirror is smooth.

• Non-mirrored surfaces have microscopic bumps so scatter the light in different directions. No image can be seen. This is known as irregular reflection.

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Plane Mirrors• To form images, light rays have to meet or

focus. • The image is laterally inverted by a plane

mirror (ie. You wave left hand, image waves right.)

• The image is upright and is the same size.• The image is virtual. It is formed behind the

mirror, in a place where no light actually went. (a real image is formed when light rays meet at a point)

Other mirror terms

• Dimished – smaller• Enlarged -

More work with the raybox…

Record what the light waves do when they hit a convex barrier and a concave barrier

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Concave Convex

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Curved Reflectors

• Concave reflectors – make the wave converge (meet at a point)

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Curved Reflectors

• Convex Reflectors – make the waves diverge (spread out)

Reflection of a pulse(animation)

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Reflection & Transmission of Pulses

• When a pulse moves from one medium into another, some of the pulse is reflected and some is transmitted.

Light to Heavy String

Heavy to Light String

How do we see the different colours in this frog’s skin? Seeing different colours

This skin absorbs all colours. No colours are reflected and so it appears black.

How do we see the different colours in this flower?

This part absorbs all colours except red and green. It reflects red and green light, and so appears yellow.

This part absorbs no colours. It reflects all the colours and so appears white.

This skin absorbs all colours except red and so is seen as red.

How do we see different colours?