Presentation on theme: "Colour (cont.d) Lesson aim"— Presentation transcript:
1 Colour (cont.d) Lesson aim To understanding that white light is made from different coloursTo understand how coloured filters work and why we see coloured objects as we do.
2 Learning OutcomesBy the end of the lesson pupils should know:how coloured filters change white lightto combine knowledge from different sources to explain how coloured filters workhow coloured objects appear in white light and in different colours of light
3 Remember: splitting white light up Until now we have used the title ‘splitting white light up’. However this process has a scientific name.The splitting of white light into a spectrum of colours is called DISPERSION.But why does white light get dispersed?
4 DispersionEach of the colours [ROYGBIV] has a slightly different waveform - what is different?They each have a different wavelength .
5 But which colour do you think is bent the most? DispersionBecause the different colours of light have different wavelengths they are bent (refracted) by different amounts.But which colour do you think is bent the most?Red light is refracted least because it has a long wavelength.Violet light is refracted the most because it has the shortest wavelength.
7 Colour : joining the colours back together Remember how you dispersed white light to give a spectrum of colours?Now do the opposite to it - you’ll need 2 prisms!A similar effect can also be seen using a colour wheel [or Newton’s disc].
9 Seeing colours How do we see objects like a book? We see objects by light striking an object and then reflecting into our eye.How do we see colour?Why does a red dress look red?Why does a green apple look green?
11 Primary ColoursYou can make any colour by mixing three colours. Do you know what they are?YellowThe colours labelled in blue text are called SECONDARY COLOURS. They can be made by mixing the primary coloursGreenRedThe colours labelled in black text are the PRIMARY COLOURS.CyanMagentaBlue
13 Red objects Why does a red snooker ball look red in white light? Remember white light is made of a spectrum of colours.The snooker ball absorbs all the colours of the spectrum EXCEPT red, so red light is reflected into our eye. The snooker ball appears red.
14 Green objects Why does a green snooker ball look green in white light? The snooker ball absorbs all the colours of the spectrum EXCEPT green, green light is reflected into our eye. The snooker ball appears green.
15 Black objects Why does a black snooker ball look black in white light? The snooker ball absorbs all the colours of the spectrum. NO light is reflected into our eye. The snooker ball appears black.
16 White objects Why does a white snooker ball look white in white light? The snooker ball doesn’t absorb any of the colours of the spectrum. The whole spectrum of light is reflected into our eye. The snooker ball appears white.
17 Why does a magenta ball look magenta in white light? Magenta objectsWhy does a magenta ball look magenta in white light?The ball absorbs all the colours of the spectrum EXCEPT red and blue, red and blue light is reflected into our eye. The ball appears to be magenta, a mixture of red and blue light.
18 Look at the clothes below. What colour light is reflected by these clothes?
19 FiltersFilters let certain colours of light pass through, but absorb all other colours.Using different coloured filters placed in front of your eye, look around the classroom and see what effect they have on your vision.filterObject
20 Red, blue and green filters … apart from red lightRed filters absorb all colours….… apart from blue lightBlue filters absorb all colours….… apart from green lightGreen filters absorb all colours….
21 Magenta, cyan and yellow filters Magenta filters absorb all colours….… apart from red and blue lightCyan filters absorb all colours….… apart from blue and green lightYellow filters absorb all colours….… apart from red and green light
23 The red light shines on the ball. Why do colours look different in different coloured light?Lets start with the example of a red ball in red light.The red light shines on the ball.The red ball reflects red light and so appears red.
24 The green light shines on the ball. What about the red ball in green light?The green light shines on the ball.The red ball only reflects red light so it absorbs the green light and reflects nothing. Because it doesn’t reflect any type of light it appears black.The green ball only reflects green light so it absorbs the red light and reflects nothing. Therefore it appears black.So what colour does a green ball appear in blue light?
25 But what if the filter you are using lets through more than one type of light. For example what will our red ball look like in magenta light.The magenta light shines on the ball. Remember that magenta is a mixture of blue and red lightThe ball reflects only red light. Therefore it absorbs the blue light and reflects the red light. It will appear to be red.
26 Over the next two slides you will be shown the a girl Over the next two slides you will be shown the a girl. She will be standing in a different coloured light each time. The colour of this light is written at the top of the slide.Your task is to choose the correct shirt and trousers to represent what those clothes would look like in each coloured light.
29 Complete the table below by adding in the colour that each object would appear to be in the conditions listed.Object (Colour)Colour FilterAppearancered ballredblueblue bookgreenmagentagreen applecyanred and blue tieredblackblackbluegreenblackred and black
30 HomeworkSuggest what clothes you would wear on a night out, where the lighting on the dance floor was mainly red and green.Draw an outfit you might wear, explaining why you chose those colours.Revise for a test next lesson
31 ActvityFlag coloursFor the flag shown, draw what it will look like in:a) Red light b) Green light c) Blue light
33 Which of the following is not a light source? The SunA starTraffic lightsA book
34 Which of the following is not seen by reflected light? Your handJupiterLight bulbThe Moon
35 Which of the following is the most dense? AirWaterGlassLead
36 When light changes direction as it moves from one medium to another we call this effect what? ReflectionRefractionDiffractionTotal internal reflection
37 It continues with no change of direction It bends towards the normal If a ray of light moves from a more dense medium to a less dense medium at an angle to the normal what happens?It continues with no change of directionIt bends towards the normalIt bends away from the normalIt stops
38 Which colour has the longest wavelength? BlueIndigoYellowRed
39 Which colour below is refracted (bent) the least by a glass prism? RedOrangeYellowGreen
40 Which of the following is not a primary colour? RedBlueCyanGreen
41 Which two primary colours make magenta? Red and cyanRed and yellowRed and blueBlue and violet
42 If white light passed through a magenta filter and then a blue filter, what colour would emerge? RedRed and blueBlueBlack
43 What colour would a red dress look in cyan light? GreenBlueBlack