Question

Tungsten has work function 4.8 $eV$ . We wish to use tungsten as photo-cathode with a 600 $nm$ wavelength. What shall we do?

• A. Coat tungsten with Cesium
• B. Oxide coat tungsten
• C. $C{u}_2$ $O_2$ be coated on tungsten
• D. None of these

Answer 1

Answer: (B)

Oxide coat tungsten

A photocathode usually consists of alkali metals with very low work function. The coating releases electrons much more readily than the underlying metal, allowing it to detect the low-energy photons in infrared radiation. To lowering the work function of the tungsten Oxide coating is used.

So, the answer is option (B).