why radio waves and gamma rays can pas through wall, but light cant?

Question

I always wondered why it was that very weak energies like radio waves can go through walls and very strong ones like gamma rays can as well, but visible light can not?

Answer 1

It has to do with the frequency of the wave and how it interacts with the material of the wall.

At low electromagnetic frequencies (long wavelength such as radio and TV), the energy transferred by the electromagnetic radiation is so low that it is only able to oscillate the free electrons that lie within the surface of metals. These waves will pass through materials like gypsum and wood with little attenuation.

The high frequency signals like xrays and gamma rays pass through the materials, but also interact with the material to heat it. X-ray imaging works by seeing what portions of the xrays were attenuated by more dense material like bone versus skin, for example.

Visible light will be absorbed because the energy will interact with the material and undergo energy transformation. Note that the energy is absorbed and the re-radiated as infrared (heat). Touch a car dashboard in the summer to get a real good example of this. The visible light and ultraviolet light from the sun passes through the glass and gets absorbed by the dashboard. The infrared light is reflected by the glass back into the car, so there is a gain of energy that heats the car.

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