Why light cannot pass through wall whereas Sound can? I have read answers stating that light is not able to be transmitted through a wall whereas sound is easily transmitted due to difference in wavelength. But, why? I am looking for detailed and satisfactory answer. Please also include the reason of WIFI signals easily transmitting through any media as compared to sound.
 A: The walls parameters
A wall has a thickness and is made from specific material. Depending from this parameters you get different results for sound and light:


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*For (window) glass it’s obvious that rather light is going through then sound.

*For a sheet of paper mainly both sound and light are going through.


The light parameters
Light is the visible part of the electromagnetic spectrum. X-rays are also part of the EM radiation as well as microwaves. Both radiations are going through room walls. To say it a little bit simplified, the EM radiation, which is going through walls, depends from the energy content of the photons (X-ray) as well as from the wavelength of the photons (microwaves or cm-waves). 
The nature of sound and light


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*Sound is the perturbation of the molecules of a gas or a solid or a liquid. Coming to your ear the change in gas pressure makes you listen sound.

*Light is emitted and get received in packages, called photons. Photons are traveling in empty space. Hitting the atoms in an obstacle they get reflected or absorbed and re-emitted. This depends from the wavelength of the light and the material of the wall.
The WiFi-signal could be stopped by sputtered glass, it will be reflected meanwhile light is going through.
