 # Visible light and the electromagnetic spectrum. we can’t see all types of light! Visible light is a very small part of a large range of radiations. It.

## Presentation on theme: "Visible light and the electromagnetic spectrum. we can’t see all types of light! Visible light is a very small part of a large range of radiations. It."— Presentation transcript:

visible light and the electromagnetic spectrum

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.

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.

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.

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

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

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.

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 =

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

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.

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

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

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