Electromagnetic Waves
Electromagnetic Spectrum
The entire EM spectrum is discussed and radio waves emitted by a transmitter are detected by a receiving antenna.
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The electromagnetic spectrum is briefly described. A transmitter together with an antenna containing a light bulb are used to demonstrate radio waves of frequency 100 MHz. The intensity of the light bulb is shown to depend on the orientation of the antenna and on its distance from the transmitter.
Visible Spectrum
A prism is used to demonstrate the visible spectrum.
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- Slide projector
- Glass prism mounted on a stand
- Screen
White light from a slide projector is passed through a vertical slit of width approximately 0.5 cm. The light then refracts through a prism and its spectrum is detected on a screen.
Primary Colors
A transparency on the overhead projector is used to demonstrate the additive and subtractive primary colors.
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- Primary colors transparency
- Overhead projector
A transparency consisting of partially overlapping primary colors is placed on an overhead projector and projected onto a screen. The additive and subtractive primary colors are thereby demonstrated. White light is shown to be produced by overlapping the three additive primaries.
Shielding of EM Waves
The shielding of radio waves is demonstrated by covering a radio with a wire cage.
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- Small transistor radio
- Faraday cage
A small transistor radio is turned on and then covered with a metal wire cage. Reception of the radio signal is shown to be attenuated while the radio is covered. The signal is restored as the cage is removed.