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Published byDennis Phillips Modified over 3 years ago

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visible light and the electromagnetic spectrum

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we can’t see all types of light! Visible light is a very small part of a large range of radiations. It is called visible light because it is the only radiation that our eyes can detect. Radio waves, infra-red, visible light, ultraviolet, x-rays and gamma rays are all part of this spectrum.

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the electromagnetic spectrum Light energy (and the other radiations) are transmitted by two waves at right angles to each other. One is a changing electric field and one is a changing magnetic field.

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what’s the difference? All electromagnetic radiation is the same. Each wave type just has a different length and frequency. Waves with a high frequency eg ultraviolet, x-rays and gamma rays have high energy. Small frequency em waves have low energy.

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the speed of light = c All of the radiations in the electromagnetic spectrum travel at the same speed. ie 300 000 000 ms -1 in a vacuum. This speed is represented by the symbol c. Each type of wave has its own length and frequency. eg red light has a wavelength of 0.00000075m and a frequency of 400 000 000 000 000 waves per second.

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speed = wavelength x frequency If you know a waves length and frequency, its speed can be determined. Work out the speed of red light using the data just provided ie frequency = 400 000 000 000 000 wavelength = 0.00000075m speed = wavelength x frequency = 0.00000075 x 400 000 000 000 000 = ms -1

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speed = wavelength x frequency If you know a waves length and frequency, its speed can be determined. Work out the speed of red light using the data just provided ie frequency = 400 000 000 000 000 wavelength = 0.00000075m speed = wavelength x frequency = 0.00000075 x 400 000 000 000 000 = 300 000 000 ms -1

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calculation Calculate the speed of light that has a frequency of 750 000 000 000 waves per second and a wavelength of 0.000 000 4m.

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calculation Calculate the speed of light that has a frequency of 750 000 000 000 waves per second and a wavelength of 0.000 000 4m. Frequency =750 000 000 000 000 Wavelength = 0.000 000 4 Speed = wavelength x frequency =

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calculation Calculate the speed of light that has a frequency of 750 000 000 000 waves per second and a wavelength of 0.000 000 4m. Frequency =750 000 000 000 000 Wavelength = 0.000 000 4 Speed = wavelength x frequency = 750 000 000 000 000 x 0.000 000 4 = 300 000 000ms -1

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determine the speed of sound by experiment I’ve got an experiment sheet that will allow you to measure the speed of light by using a microwave oven and a dish of marshmallows!! See me if you want to try this at home.

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an electromagnetic family Open to page 159 of Jacaranda Science book 3 and use the information on pages 158 and 159 to answer the questions Remember Q 1, 2 and 3. Attempt Imagine on page 159

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light energy is transmitted by waves light reflects like other waves light refracts like other waves

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