Question: What is the photoelectric effect?

Answer: The photoelectric effect is a phenomenon in which electrons are emitted from the surface of matter (usually metals) when light shines upon it. Einstein explained the effect by proposing that light consists of small particles, or quanta, called photons, which carry energy that is proportional to the frequency of light. The electrons in the matter that absorb the energy of the photon get ejected. These findings were published in 1905 in the paper “On a Heuristic Viewpoint Concerning the Production and Transformation of Light”. Einstein’s observations that the photoelectric effect could only be explained if light behaves like a particle, not a wave, was instrumental in establishing the hypothesis that light can behave both like a wave and a particle.

Question: What are the practical applications of the photoelectric effect?

Answer: The photoelectric effect is very important for our daily life. It is the basis for photosynthesis, which is like a very effective solar cell where sunlight is absorbed by plants to make them grow. The effect also forms the basis for a variety of devices such as photodiodes, which are used in light detection within fibre optics, telecommunications networks, solar cells, imaging and many other applications.