Physics 幾問,請入

Q1) X-ray can penetrate very very thin metal sheet and so cannot penetrate general metal objects. Therefore, it cannot detect hidden flaws in metal structure. But gramma ray can penetrate almost all metal plate and detect these flaws. (Ultrasonics, of frequency higher than audiable one, can also detect these flaws by reflection but not by penetration. Moveover, they travel much slower than X-ray and the time of travel can be easily measured.)

Q2) I think the ray as electromagnetic waves (e.m. waves). They have particle property and are called Photons. By Planck's theory, a photon carries higher energy when the ray have higher frequency. Higher energy photons, e.g. gramma rays, have higher penetrating power because they have much higher than atoms' energy levels involved and are less interaction with atoms, i.e. passing through without changing direction.

X-ray has shorter wavelength which cannot penetrate deep into metals. Hence it cannot be used to detect hidden flaws in metal structure. Insteadm ultrasonics can be used for this purpose.