X-rays and visible light have different properties that determine their interaction with matter, including how they penetrate through objects. The ability of X-rays to pass through the human body while visible light cannot is due to differences in their wavelengths and how they interact with atoms and molecules.
X-rays have much shorter wavelengths than visible light. The wavelength of X-rays typically ranges from 0.01 to 10 nanometers, while visible light has wavelengths between 400 and 700 nanometers. The shorter wavelength of X-rays allows them to interact more readily with the tightly bound inner electrons of atoms.
When X-rays pass through matter, they can undergo a process called attenuation, which involves absorption and scattering. Absorption occurs when X-ray photons are absorbed by the atoms or molecules in the material. Scattering happens when X-ray photons change direction after interacting with the electrons in the material.
In the case of human tissues, X-rays can penetrate through the body because they experience less absorption and scattering compared to visible light. This is because the energy levels of X-rays are higher, and they interact more strongly with the electrons in the atoms of the body's tissues. However, some X-rays do get absorbed or scattered, and this is what allows X-ray imaging techniques like radiography to work.
On the other hand, visible light interacts differently with matter. When visible light encounters an object, it can be absorbed, reflected, or transmitted. In the case of human tissues, visible light is mostly absorbed or scattered rather than transmitted through the body. This absorption and scattering of visible light by the atoms and molecules in our tissues is what gives us the ability to see objects around us.
So, the main difference between X-rays and visible light lies in their wavelengths and how they interact with matter. X-rays, with their shorter wavelengths and higher energy, can more easily pass through the body's tissues due to their ability to penetrate and interact with the inner electrons of atoms. Visible light, with its longer wavelengths, is mostly absorbed or scattered by the atoms and molecules it encounters, which is why it cannot penetrate through the body like X-rays can.