WAVE MODEL & COLOURS

LIGHT: Particles or Waves?

• Wave Model of Light–Explains most properties of light–Uses both light and waves to

transfer energy, and they both go outward in all directions from their source.

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PRISM A transparent glass or plastic object with flat, polished

sides. The light separates into the colours of the rainbow,

including red, orange, yellow, green, blue, and violet. The range of different colours of light is called the VISIBLE

SPECTRUM.

WAVELENGTH & COLOURS

each colour has a different wavelength and frequency RED LIGHT- longest wavelength; lowest frequency in

visible light VIOLET LIGHT- shortest wavelength; highest frequency in

visible light.

COLOUR FREQUENCY (Hz) WAVELENGTH (nm)

Red 4.3 X 1014 700

Orange 5.0 X 1014 600

Yellow 5.2 X 1014 580

Green 5.7 X 1014 550

Blue 6.4 X 1014 450

Violet 7.5 X 1014 400

• Transparent Objects: – Light transmitted because of no scattering– Color transmitted is color you see. All other

colors are absorbed.

• Translucent: – Light is scattered and transmitted some.

• Opaque: – Light is either reflected or absorbed. – Color of opaque objects is color it reflects.

Color of Light

ADDITIVE COLOUR THEORY OF LIGHT

Is when white light is compressed of different colours (wavelengths) of light.

It is possible to produce white light by combining only 3 colours.

PRIMARY COLOURS: Red, Green, Blue If you mix correct amounts of all three primary colours of

light, you will make white light. If you mix only two of the primary colours together you will

make a secondary colour.

SECONDARY COLOURS: Magenta, Yellow, and Cyan.

PRIMARY COLOURS

SUBTRACTIVE COLOUR THEORY

• When light wave strikes an object, some wavelengths of light REFLECT, meaning they bounce off the object.

• Other wavelengths are absorbed.

• The colour you see when you look at an object depends on the wavelength that are reflected.

• Ex: A red rose reflects red wavelengths of light and absorbs other colours.

SUBTRACTIVE COLOUR THEORY CONT’D

Subtractive Colour Theory states:• coloured matter selectively absorbs different colours or

wavelengths of light.• the colours that are absorbed are ‘subtracted’ from the

reflected light that is seen by the eye.• a black object absorbs all the colours.• a white object reflects all colours.• a blue object reflects blue and absorbs all other colours.• Primary subtractive colours: magenta, cyan, and yellow.• Secondary subtractive colours: red, green, blue

• Green, blue, red• Complimentary

pigments are primary colors for light!

Complementary Pigments

Paint Pigments

–Pigments absorb the frequency of light that you see

–Primary pigments• Yellow + cyan + magenta =black• Primary pigments are compliments

of the primary colors of light.

LEARNING CHECKPOINT!!!!

1. What property of a light wave determines the colour of light?2. List the 6 general categories of colour from the longest wavelength

to the shortest wavelength.3. What is the visible spectrum?4. What properties of light does the wave model of light explain?5. What does the additive colour theory of light state?6. What does the subtractive colour theory of light state?7. A balloon appears yellow when seen in white light. Explain the

colour it will appear in: (a) green light

(b) magenta light