1.4: Electromagnetic waves
- Page ID
- 128439
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Using UHF radio waves, we measure c using standing waves; we transmit UHF waves in the vertical direction and reflect the downwards-going waves with a conducting plane on the ground. We map the resulting electric field with a moveable receiving antenna. We show that the electric field is at right angles to the direction of propagation, which defines the plane of polarisation. Interference of incident and reflected waves gives the wavelength, and with the oscillator frequency this gives c. EM waves require no medium. c relates space and time in the theory of relativity, discussed in a later chapter.
- Standing wave measurement of c using UHF.
- EM waves require no medium
- c relates space and time.
| Links to related material (more coming soon) | |
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| Why vision? Why vision? Why the importance of the 400 to 700 nm band? Why so little UV and IR vision? Why no bio-radar? How does vision compare with hearing? |
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| Colour mixing Additive colour mixing by projection. Additive colour mixing on RGB monitors and phones. Newton's colour wheel. Subtractive primaries and subtractive colour mixing. Details of the experiments from the multimedia chapter. |
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| Electromagnetic transverse waves The direction of the electric and magnetic fields: transverse or longitudinal. Experiments with UHF radio. Polarised light and polarizing sun glasses. Details of the experiments from the multimedia chapter. |
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| Molecules and photons Quantisation of light - and of water! Light and photons. Photon energy depends on wavelength. Black body radiation. |
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| Newton's prisms Light and prisms: refaction, dispersion and recombination. |
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| Shadows:particles and waves Light shadows and particle shadows: the particle model for light. Wave shadows and their dependence on wavelength. Diffraction and wavelength. Comparison of sound and light. |
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| Speed of light A simple measurement of the speed of light by time of flight. Pulsed laser, beam splitter and mirrors, detectors, oscilloscope. Details of the experiment from the multimedia chapter. |
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| Speed of Radio Waves Measuring the speed of radio waves using standing waves in UHF. Oscillator, dipole transmitting and receiving antennae, oscilloscope. Reflections from a conductor, standing waves, nodes. Details of the experiment from the multimedia chapter |
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Young's experiment - water waves and light |
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