Stories from Physics for 11-14 14-16
For centuries, glass has been used to make lenses that refract visible light. As the frequency of radiation increases, waves are refracted less when travelling between media so it had been assumed that gamma ray lenses were not a realistic possibility. However, in the 1990s, it was found that X-rays could be diffracted by beryllium, and carbon lenses and gamma ray lenses have been constructed from silicon and gold. It is believed that short-lived electron-positron pairs generated by the electric fields of the nuclei in the lens interact with gamma radiation to change its path. It is hoped that the gamma ray lenses will have applications in medical diagnosis, for example, in tracking the absorption of the anti-depressant medication, lithium.