Question

The xerographic (dry writing) process was invented in $\mathbf{1938}$by C. Carlson. In xerography, an image is produced on a photoconductor by exposing it to light. Selenium is commonly used, since its conductivity increases three orders of magnitude upon exposure to light in the range from$\mathbf{400}$to$\mathbf{500}\mathbf{}\mathit{n}\mathit{m}$. What color light should be used to cause selenium to become conductive? (See Figure$\mathbf{12}\mathbf{.}\mathbf{3}$)

Short answer

The light that will allow selenium to be conductive is purple or green.

Step-by-step solution

Define Elements

An element is a pure material made up solely of atoms with the same number of protons in their nuclei.

Obtaining color that will be used by selenium to be conductive

Taking a look into visible spectrum of light we will observe that between$400nm$ and$500nm$ the colors are purple and green. The light will then interact with the matter producing excitation of electrons in the molecular level and we can see that the changes will occur.

Therefore, green and purple light will excite selenium electrons.