The shorter the wavelength the greater the penetration. So why do radio waves go through walls but not light?

Answer 1

Incorrect deduction from too broad of a premise.
From "How Things Work":

"Transmission - If the frequency or energy of the incoming light wave is much higher or much lower than the frequency needed to make the electrons in the material vibrate, then the electrons will not capture the energy of the light, and the wave will pass through the material unchanged. As a result, the material will be transparent to that frequency of light.
Most materials are transparent to some frequencies, but not to others. For example, high frequency light, such as gamma rays and X-rays, will pass through ordinary glass, but lower frequency ultraviolet and infrared light will not.
In absorption, the frequency of the incoming light wave is at or near the vibration frequency of the electrons in the material. The electrons take in the energy of the light wave and start to vibrate. What happens next depends upon how tightly the atoms hold on to their electrons. Absorption occurs when the electrons are held tightly, and they pass the vibrations along to the nuclei of the atoms. This makes the atoms speed up, collide with other atoms in the material, and then give up as heat the energy they acquired from the vibrations.
The absorption of light makes an object dark or opaque to the frequency of the incoming wave. Wood is opaque to visible light. Some materials are opaque to some frequencies of light, but transparent to others. Glass is opaque to ultraviolet light, but transparent to visible light. "

The same is true of radio waves -- they will penetrate SOME things, but not all things. Hope this helps!

Answer 2

Your premise is wrong.

Penetration depends on absorbtion - so it depends on the interaction between EM radiation at a given wavelength and the material.

Generally, longer wavelengths penetrate much better.

For instance, infra red penetrates the skin deeper than UV. Beta particles (with very, very short de Broglie wavelengths) get nowhere near as far as gamma rays. Red light penetrates fog better than blue. And so on.

Answer 3

Unless your walls are made of glass the photons are reflected from the surface thereby illuminating the object. Radio waves also are reflected from solid objects (RADAR) .

Both light and radio encounter materials which are both opaque and /or transparent , depends on the material you consider.

Answer 4

Walls absorb light, unless you have windows, then the light will go through the glass.

Answer 5

Light waves are in the visible spectrum.