放射輻射的穿透能力愈大，對人體的傷害愈大?

High penetrating radiaiton (x-ray or gamma ray) poses great radiation hazard as conpared with low penetrating radiation, (alpha and beta). When alpha radiation incident onto human body, it really cannot penetrate the skin, thus causing no hazard to internal organs.

Beta radiation can only penetrate into some distance into the skin, thus only causes skin hazard. It also brings not much harm to internal organs, except those high energy betas, which could cause a certain amount of organ doses.

However, gamma or x rays can penetrate deep into the body. This brings hazards to most, if not all, internal organs.

In terms of organ risk, human skin can "tolerate" higher does of radiation than internal organs (such as lung or stomach). The International Commission on Radiological Protection (ICRP) recommends an annual dose limit of 500 mSv to skin, but only a public dose limit of 1 mSv to the body as a whole. This is the reason why externally, highly penetrating radiation is more dangerous than low penetrating radiation.