Exciting Facts About Light and CdS Crystal Interaction

What happens when light from a hydrogen discharge tube is incident on a CdS crystal?

a) The light is absorbed
b) The light is transmitted

Answer:

b) The light is transmitted

When light from a hydrogen discharge tube is incident on a CdS crystal, an interesting interaction takes place. The CdS crystal, also known as Cadmium Sulfide, behaves in a particular way when exposed to light due to its unique bandgap energy.

The light that is transmitted through a CdS crystal depends on its bandgap energy. In this case, the bandgap energy of CdS is approximately 2.4 electron volts (eV). The CdS crystal absorbs light with energies greater than its bandgap and transmits light with energies lower than its bandgap.

Since the incident light is from a hydrogen discharge tube and consists of a broad spectrum of wavelengths, including the visible light spectrum, the CdS crystal selectively transmits certain wavelengths. Specifically, any light with energies below 2.4 eV (corresponding to longer wavelengths) will be transmitted through the CdS crystal.

Therefore, when light from a hydrogen discharge tube is incident on a CdS crystal, the longer wavelength light, or the light with lower energies than 2.4 eV, will be transmitted through the crystal. This interaction showcases the fascinating properties of CdS crystals in interacting with light based on their bandgap energy.