Imaging principle of x-ray film.

x-rays are electromagnetic radiation with a short wavelength between ultraviolet rays and gamma rays. It was discovered by German physicist W.K. Roentgen in 1895, so it is also called Roentgen ray.

Perspective reasons

Roentgen rays have high penetrating power, and can penetrate many substances that are opaque to visible light, such as ink paper and wood. This kind of invisible ray can make many solid materials have visible fluorescence, make photographic negatives sensitive and ionize the air.

generally speaking, larger atoms have a greater chance of absorbing X-ray photons. Human soft tissues are composed of finer atoms and bones contain more calcium ions, so bones attract more X-rays than soft tissues. Therefore, X-rays can be used to examine human structures.

imaging results

after a photographic negative is placed in a human body, X-rays will pass through the soft tissues (skin and organs) in the human body and irradiate the negative, so that these parts will remain black after the negative is developed; X-rays cannot pass through hard tissues in human body, such as bones or other injected substances containing barium or iodine, and the negative film will appear white after development.