What is X-ray? How was it discovered?

X-rays are a kind of light, but this kind of light is different from the light we usually understand, it can pass through some objects behind the human body, but the eyes cannot see it,light is actually the transfer of energy, and its essence is a flow of photons in a specific frequency band,the light source emits light because the electrons in the light source gain extra energy and release energy in the form of waves during the transition process.

Roentgen discovered X-ray

In the long-term evolution of the human eye, it is only sensitive to the frequency band of about 380~780nm, so the electromagnetic wave of this specific frequency band is called visible light,in addition to visible light, there are many lights invisible to the human eye, such as radio waves, infrared rays, ultraviolet rays, X-rays, and gamma rays. These lights are all of a certain band and frequency in the electromagnetic spectrum,these invisible lights have low and high energy, and visible light is in the middle band,light with lower energy than visible light includes radio waves (including long-wave, medium-wave, short-wave, and microwave) and infrared rays,light with higher energy than visible light includes ultraviolet rays, X-rays, and gamma rays.

Spectrum of some common light

X-rays are electromagnetic waves second only to γ-rays, with a wavelength between 10 nanometers and 0.01 nanometers, a frequency between 3^16 and 3^20 Hz, and an energy of 124eV~1.24MeV,this is the energy of each photon, which belongs to high-energy rays, so the penetrating power is very strong. When X-rays irradiate the human body, some of them are absorbed by the human body, and most of them pass through the atomic gaps.