X光中的顏色represent what !!1

I presume you ask about the [white and black areas] on X-ray films.

X-ray, because of its short wavelength, can penetrate the human body. The absorption of X-rays in bone and tissues are different. Bone, because of its higher density, absorb X-rays much better than soft tissues.

When a beam of X-ray incident onto the body, bones absorbs X-rays far more than tissues. The emergent X-ray is then made to fall onto a film. Thus X-rays passing through the bones will be of lower intensity than those through tissues, causing weaker exposure to the film. On the other hand, X-rays passing through organ tissues causes higher exposure on the film.

After the exposed film is developed, areas where high exposure has taken place (for X-ray through tissues) will appear black, whereas areas where low exposure has taken place appears white. This is the reason why in a chest X-ray film, the lung tissues appear as black on the film and the ribs appear as white.

[Note: an unexposed film, after developed, will appear black. An exposed film appaears white after developed.]