The spectrum
Radio waves, the warmth you feel from a heater, the light you see, X-rays and gamma rays are all the same thing: electromagnetic radiation. The only difference is the size of the wave, and with it the energy of each photon. All travel at the same speed in a vacuum. The band our eyes see is less than a thousandth of the whole, and it is no accident that it falls exactly where the Sun emits most and where the atmosphere lets light through: we see what was worth seeing to survive here, not what is there.
Where this sits
- Comes after
- Radiation
Exercises from this rung
Generated by the app, from easiest to hardest
Which part of the spectrum do our eyes see?
- Visible light
- Ultraviolet
- Infrared
- Almost all of it
Why A tiny band, from red to violet, less than a thousandth of the whole spectrum. That is no accident: it is exactly where the Sun emits most and where the atmosphere lets light through. We see what was worth seeing to survive here, not what is there.
easierHow fast do radio waves travel compared with visible light?
- The same
- It depends on the power
- Much slower
- Much faster
Why The same, 300,000 km/s: they are the same thing at a different wavelength. That is why a radio command to a probe on Mars takes exactly as long as a flash of light would, between four and twenty minutes depending on where the planet is.
in betweenWhich carries most energy per photon?
- Infrared
- Radio waves
- Visible light
- Gamma rays
Why Gamma, because a photon's energy grows as the wave gets shorter. That is why they are the dangerous ones and radio waves are not, however much power they carry: a billion radio photons still cannot break a single molecule.
harder