Final answer:
Lanthanum oxy-bromide crystals emit green light when used in X-ray intensifying screens, aiding in medical imaging by converting X-ray energy to visible light. In the context of color TVs, a cathode ray tube uses a 30-kV accelerating potential, which could lead to the creation of X-rays, but shielding is employed to protect viewers.
Step-by-step explanation:
Lanthanum oxy-bromide rare earth crystals in intensifying screens are known for emitting light in the green part of the spectrum when energized. This technology is often used in healthcare settings, specifically in X-ray intensifying screens. The crystals absorb X-ray energy and convert it into visible light, which then exposes the X-ray film. These screens are used to improve the efficiency of the imaging process since they require less exposure to X-rays to obtain a clear image. The technology is particularly important because it minimizes the radiation dose to the patient.
When it comes to color televisions, a similar process happens where a cathode ray tube (CRT) uses an accelerating potential (in the case presented, a 30-kV potential) to send electrons towards the phosphor-coated screen. These electrons stimulate the phosphor compounds to emit visible light that forms the picture. While primarily the electrons produce visible light to generate images, some of the energy can also result in the production of X-rays. However, shielding is provided around CRTs to protect viewers from any X-ray emissions.