††††X-rays are an invisible form of radiation of very short wavelength. X-rays can pass through many materials that stop ordinary light rays. Some substances. such as bone, absorb more X-rays than softer tissues like skin and muscle. This fact is used when studying special X-ray pictures of the body. The bones show up clearly as white areas, and soft tissues as grey areas. Doctors use X-ray pictures to detect diseases, broken bones and foreign bodies, while dentists use X-rays to examine growing teeth. X-rays have many other uses, though. X-rays can be used to check machinery for cracks and faults, while security staff at airports use X-rays to check luggage for weapons and bombs. Chemists use X-rays to study how atoms are arranged in crystals and other substances, while astronomers can learn more about the stars by studying the X-rays that come from them.
