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LIGHT & THE ELECTROMAGNETIC SPECTRUM

Explore the properties of waves and energy transfer in white light, the electromagnetic spectrum, and the wave model of light. Learn how colors are formed and the theory behind additive and subtractive color mixing.

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LIGHT & THE ELECTROMAGNETIC SPECTRUM

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  1. LIGHT & THE ELECTROMAGNETIC SPECTRUM

  2. LIGHT AND COLOUR What is WHITE LIGHT made of?

  3. LIGHT AND COLOUR • White Light • Light that appears white to the eye, composed of some combination of light with frequencies in the red, blue, and green parts of the spectrum

  4. ENERGY IN A WAVE • Wave • Is a disturbance that transfers energy from one point to another without transferring matter. • In a water wave, energy passes through the water from one point to another as the wave rises and falls. • This energy allows the wave to do work.

  5. ENERGY IN A WAVE • Wave • Imagine that a duck sits on the surface of a lake. • The duck moves up and down with the wave, which means that the wave transfers energy to the duck.

  6. ENERGY IN A WAVE • Wave • The water moves up and down, but the water does not move forward with the wave. • Only energy moves forward. Water and the duck move up and down with each wave. Energy moves forward.

  7. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) • Highest point of the wave is called a crest. • Lowest point of a wave is called a trough. • The level of the water when there are no waves is called the rest position.

  8. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) Amplitude Wavelength Rest Position

  9. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) • Wavelength • The distance from crest to crest. • Standard symbol for wavelength is . • Wavelength is measured in meters.

  10. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) • Amplitude • Wave height (from the rest position of the wave to the crest or the wave depth from the rest position to the trough. • The energy transferred by a wave depends, in part, on it amplitude.

  11. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) Amplitude Wavelength Rest Position

  12. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) • Amplitude • The larger the amplitude, the more energy that is carried. • The smaller the amplitude, the less energy that is carried.

  13. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) • Frequency • The rate of repetition of a wave. • For example, if wave crests pass the dock 10 times in a minute, the frequency of the wave is 10 cycles per minute.

  14. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) • Frequency • The higher the frequency, the more energy the wave passes along. • The standard symbol for frequency is f. • It is measured in hertz (Hz), which is cycles per second.

  15. ENERGY IN A WAVE • Properties of Waves (how waves transfer energy) Amplitude Wavelength Rest Position

  16. ENERGY IN A WAVE • Mathematical relationship among the speed v, the frequency f, and the wavelength . • v = f x  • For example, if the wavelength of a wave is 5cm and the frequency is 10 cycles/s, then the speed is • v = 10 x 5 • = 50 cm/s

  17. THE ELECTROMAGNETIC SPECTRUM • Light is a form of energy. • Visible light is only a tiny fraction of the energy that surrounds us every day. • We are also surrounded by invisible light-like waves, which together with visible light are called electromagnetic radiation.

  18. THE ELECTROMAGNETIC SPECTRUM • Electromagnetic radiation is a wave pattern made of electric and magnetic fields that can travel through empty space. • The entire range of electromagnetic radiation extends from the shortest gamma rays to the longest radio waves and includes light. • This range is called electromagnetic spectrum.

  19. Low energy High energy Low Frequency High Frequency The Electromagnetic Spectrum X-Rays Radiowaves Microwaves Ultra-violet GammaRays Infrared . Long Wavelength Short Wavelength Visible Light

  20. THE WAVE MODEL OF LIGHT • This model is used to show similarities between light and the movement of waves on the surface of water to explain several properties of light that we can see. • When light is shone through a prism the light separates into the colours of the rainbow – red,orange,yellow,green,blueandviolet.

  21. Prism • White light is made up of all the colors of the visible spectrum. • Passing it through a prism separates it.

  22. If the light is not white • Passing this light through a prism does something different.

  23. Additive Colour Theory of Light • White light is composed of different colours (wavelengths) of light. • All three primary colours together produce white light. When paired they can create magenta, yellow and cyan.

  24. SUBTRACTIVE COLOUR THEORY OF LIGHT • When a light wave strikes an object, some wavelengths of light reflect. Others are absorbed. • The colours that are absorbed are subtracted from the reflected light that is seen by the eye.

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