Question

What purpose does a photo-cathode serve?

1) To emit electrons when exposed to light
2) To absorb photons and convert them into electrical energy
3) To amplify the intensity of light
4) To filter out unwanted wavelengths of light

Answer 1

A photo-cathode serves to emit electrons when exposed to light, utilizing the photoelectric effect, and is often used in devices like photomultiplier tubes to generate detectable electrical signals.

Step-by-step explanation:

The purpose of a photo-cathode is to emit electrons when exposed to light. This is related to the photoelectric effect, where light energy, or photons, is absorbed by the photo-cathode material causing it to release electrons. Photo-cathodes are commonly used in devices like photomultiplier tubes, where cascades of electrons generated via the photoelectric effect are multiplied to produce a significant electrical signal. For instance, in photomultipliers, each ejected electron is accelerated toward dynodes with increasingly positive potential, resulting in a multiplication of electrons and a detectable output current proportional to the light intensity.