Warm-Up

• Use a ray diagram to explain how light behaves differently when it contacts:– A rough object vs a smooth object?– An opaque object vs a transparent object?

How We See Colour

LG: I can explain how light interacts with objects to produce the colours we see

Seeing Colour of Opaque Objects• All of the “invisible” colours of white light (ROY G. BIV) shine

on the objects we see• Opaque objects absorb some colours and reflect others• The colour that an opaque object appears is determined by

the wavelength of light it reflects (ie. The banana is yellow because it reflects yellow light)

Seeing Colour of Transparent and Translucent Objects

• Like opaque objects, transparent and translucent objects absorb all colours except the one(s) we see

• Translucent and transparent objects also transmit the same colour they reflect

Seeing Black and White• Objects appear black when all colours are absorbed• Objects appear white when all colours are reflected

Activity: Spotlight on Colour1) Write a word or draw a picture on white paper using

a blue pen2) Predict whether the drawing will be more visible

under white light or blue light. Give reasons for your choice.

3) Dim the lights in the room and test your prediction. 4) Predict how the drawing will look under red light

and test your prediction.5) Draw a ray diagram to explain your observations in

steps 3 and 4

Learning Check Point…

• Is it better to wear black clothing or white clothing on hot summer days? Why?

• If you shine a red light on a green pepper, what colour would it be? Use a ray diagram to explain your answer.

• Choose two objects in the room and use a ray diagram to explain the appearance of their colour