Suppose a sample of strontium-90 is stored in a lead container with lead walls. It is know that X-ray radiation may be detected outside the lead container. After some discussion with my peers, it seems that we have differing theories on how the X-ray radiation is formed.
- Beta particles emitted by the decay of strontium-90 collide with the walls of the container, and in the process emit photons. These photons, when energetic enough, have high penetration power and can penetrate the walls of the container.
- Similarly, the beta emission by the decay of strontium-90 produces photons, but the photons instead tunnel through the walls.
The first theory seems to show a picture of the emitted x-rays actually passing through the empty space between lead particles in the wall of the container. Under this theory, the term "penetration" is not well defined enough.
Under the second theory, it seems that quantum tunnelling is not directly applicable because there is no potential barrier involved.
Which would be the correct explanation, or is there a better explanation?