What type of radiation passes through 1 cm of lead

The radiation emitted by the radioactive rock is:. You should have noticed that some of the radiation is absorbed by the sheet of paper. This suggests that some of the radiation from the rock is alpha radiation. Then you should have noticed that when the rock is wrapped in a thick layer of aluminium foil the count rate of the radiation detected is reduced. This suggests that some of the radiation from the rock is beta radiation.

You should also have noticed that even when the rock is wrapped in the thick layer of aluminium foil some radiation is still being detected. The ionizations they cause are very close together - they can release all their energy in a few cells. This results in more severe damage to cells and DNA. These particles are emitted by certain unstable atoms such as hydrogen-3 tritium , carbon and strontium Beta particles are more penetrating than alpha particles, but are less damaging to living tissue and DNA because the ionizations they produce are more widely spaced.

They travel farther in air than alpha particles, but can be stopped by a layer of clothing or by a thin layer of a substance such as aluminum. However, as with alpha-emitters, beta-emitters are most hazardous when they are inhaled or swallowed. Unlike alpha and beta particles, which have both energy and mass, gamma rays are pure energy. Gamma rays are similar to visible light, but have much higher energy. Gamma rays are often emitted along with alpha or beta particles during radioactive decay.

Gamma rays are a radiation hazard for the entire body. They can easily penetrate barriers that can stop alpha and beta particles, such as skin and clothing. Gamma rays have so much penetrating power that several inches of a dense material like lead, or even a few feet of concrete may be required to stop them.

Gamma rays can pass completely through the human body; as they pass through, they can cause ionizations that damage tissue and DNA. Because of their use in medicine, almost everyone has heard of x-rays.

X-rays are similar to gamma rays in that they are photons of pure energy. X-rays and gamma rays have the same basic properties but come from different parts of the atom. X-rays are emitted from processes outside the nucleus, but gamma rays originate inside the nucleus. Because their masses are identical to the scattering electrons, large deviations in the beta particle path are possible, and even thin absorbers will attenuate betas by virtue of the fact that they readily get scattered out of the direct beam.

The low energy betas are rapidly attenuated. C gives off betas with a maximum energy of 0. The maximum range of C betas is only 0. We have both sources and it's nice to contrast them. A Harvard ID card is about 0. Not so when you switch over to the Sr source. The lack of charge eliminates Coulomb interactions and allows gamma rays to be much more penetrating.

The interactions that do occur are by way of the photoelectric effect, Compton scattering, and pair production. The probability for any of these happening is specified by a cross section, and the linear attenuation coefficients for gamma rays are defined by these cross sections.

Unlike charged particles, a certain percentage of gammas will always make it through the absorber, and it is useful to consider the half-value thickness of a given absorbing material for the gamma ray energies of interest.

The half-value thicknesses are determined from Equation 1 using the linear attenuation or mass attenuation coefficients found in the references below. This causes the release of ionising radiation which allows the nucleus to become more stable. Atoms that do this are said to be radioactive. A comparison of alpha, beta and gamma.

Penetrating power Each type of radiation has a different ability to penetrate materials. The range of the alpha radiation in an absorbing material is less than that of beta or gamma. The alpha radiation transfers more energy to an absorber than beta or gamma radiation. Alpha radiation is absorbed by the thickness of the skin or by a few centimetres of air. Beta radiation is more penetrating than alpha radiation.