Radio waves are able to diffract readily around buildings, .......?

Question

as anybody with a portable radio receiver can verify. However, light waves, which are also electromagnetic waves, undergo no discernible diffraction around buildings. Why not?

Answer 1

to elaborate on the first answer, the wavelength of light is too small to diffract around a building, they are much much smaller than the wavelengths of radio waves.

Answer 2

Radio waves are not able to diffract around buildings, however, due to the wave legnth of a radio wave, most of the wave gets past the building. Light does not because the electromagnetic wave is much shorter. Just like a radio wave can pass through the ground (ground wave effect) and light cannot. Also, both waves will reflect off the building or the ground, refraction which then causes you to see the light and in radio waves can cause the wave to bounce around the world as a morse code signal can do under the right circumstances.

Answer 3

Because of their wavelength.

The diffraction behavior of any electromagnetic wave (radio, microwaves, light, gamma rays, etc) is closely linked to it's wavelength. When a diffraction aperture is significantly larger than the wavelength passing through it, very little diffraction takes place.

Visible light (red-to-violet) has a wavelength varying from 380nanometers for red to 780 nanometers for violet (a nanometer is one billionth of a meter).

Radio waves vary from over 100,000 kilometers (yes, kilometers!) down to 100 Millimeters. This is much MUCH bigger than the wavelength of visible light.

As a reult it takes a much smaller diffraction grid to produce diffraction of visible light, but radio waves are huge enough to diffract around things like buildings.

Answer 4

It is the wave length which governs the ability to travel through objects. Check out the glass window on your microwave oven which has a whole bunch of holes which the micro waves cannot penetrate.