4.2 Properties of Visible Light Date: (pages )

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1 4.2 Properties of Visible Light Date: (pages ) Visible light is a mixture of all the colours of the rainbow. A prism refracts light separating the colours. A second prism can recombine the colours to form white light. Different colours of the light are carried by light waves that have different wavelengths. An object looks blue in sunlight because it reflects blue and absorbs colours other than blue from the sunlight. Wave model of light is a way of explaining how light behaves. The wave model of light pictures light. Refraction of light: p.145 If light is travelling at an angle and the speed that light travels is different in the two materials, the wave will be bent (refracted!) Refraction is the White light (such as ) has all light waves of different wavelengths and frequencies. Different wavelengths refract differently when they enter a new medium (example: a prism!). The longer wavelengths are refracted than the shorter wavelengths, therefore. The colour always bends the least and the colour always bends the most.

2 When it rains, raindrops refract sunlight and a rainbow can form. In order of decreasing wavelength and increasing frequency, the colours of the rainbow are: R O Y G B I V This range of colours is called the, the wavelengths range is Reading check p Colour and Reflection: p.148 Reflection occurs when. When sunlight strikes a surface, some colours. Only the reflected colours can be seen! If there is no light (for example in a dark room) there can be no colours. Three colours of light are needed to produce all the colours that can be seen. The colours are. When these three colours are combined in just the right amount, is produced.

3 4.3 Light and the Electromagnetic Spectrum (pages ) A rainbow or visible spectrum is a tiny portion of a much larger spectrum of radiation called the electromagnetic spectrum. Radio waves and infrared radiation have longer wavelengths, lower frequencies and less energy than visible light. Ultraviolet light, X-rays, and gamma rays all have shorter wavelengths, higher frequencies and more energy than visible light. Each region of the invisible spectrum has special properties that make it useful in some sort of imaging technology. No matter where we are, we are surrounded by invisible waves. Familiar examples of waves from the electromagnetic spectrum that we use every day:. Beyond Visible Light: p. 153 The sun generates much more than just sunlight! In addition to the light we can see, the sun also. (what is the definition of energy?) The light that we see is just a tiny band of a much broader spectrum of energy.

4 Electromagnetic radiation: p. 154 Why is light called electromagnetic radiation? In a water wave, individual water particles move up and down as the wave passes. In a light wave it is. Electromagnetic radiation is Wavelengths Longer than Visible Light: p. 154 Radio Waves come in various wavelengths. Some uses of radio waves are Microwave frequencies can be used to warm up our food or communicate between earth and satellites in orbit. Our microwave ovens use a specific frequency that is Radar can be used for tracking the movement of and also because raindrops, ice crystals, etc. reflect radio waves differently and these readings can be analyzed to make weather predictions. Infrared Waves are used by TV remotes to communicate with a TV, as an example. But infrared radiation is also referred to as. Every object emits some kind of infrared energy, as all objects contain some heat energy. which emit infrared radiation are used in restaurants to keep food warm. Reading check p.157 #1-5

5 Wavelengths Shorter than Visible Light: p.158 These wavelengths have than visible light. Ultraviolet Waves are found just beyond the visible spectrum. This radiation is required for us to make but too much can lead to. UV waves have other uses as well. They can be used in fluorescent fabrics, forensic work, and sterilization. UV waves X-rays are energetic enough to pass through our bodies and can be used to take images of internal structures. X-rays can also be used to. Gamma rays are the shortest wavelength and highest frequency and energy portion of the EM spectrum. Gamma rays are produced in and also the hottest regions of the universe. Focused beams of gamma rays are used in radiation therapy to kill. Reading check p. 160 #1-5

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