Photoelectric

Photoelectric, in physics, describes a phenomenon where electrically charged particles, most often electrons, are emitted from or within a material when it absorbs electromagnetic radiation, such as light. This process, also known as the photoelectric effect, demonstrates the particle nature of light, as energy is transferred in discrete packets called photons. The number of emitted particles depends on the intensity of the light, while their kinetic energy is dictated by the frequency, or colour, of the light source, not the light's intensity. This fundamental principle is used in various technologies, including light sensors, solar panels, and image sensors.

Photoelectric meaning with examples

• Solar panels utilize the photoelectric effect; photons from the sun strike semiconductor materials like silicon, liberating electrons and generating an electrical current, converting light energy into usable electricity. The efficiency of a panel depends on the material used and is maximized when the photons carry the right amount of energy to release the electrons.
• The photoelectric sensor in an automatic door uses a light beam and a detector. When an object interrupts the beam, the detector senses the absence of light due to the photoelectric effect, triggering the door to open. The sensitivity can often be adjusted to avoid unwanted triggers.
• In older, now largely obsolete, photographic light meters, the photoelectric effect in a photovoltaic cell would generate a small current proportional to the incident light intensity. This current would then drive a meter needle, giving an indication of the brightness and thus, the required settings for correct camera exposure.
• Advanced image sensors, used in digital cameras and smartphones, use the photoelectric effect. Each photosite (or pixel) is made of a material that absorbs light and releases electrons; the number of electrons released indicates the light intensity for that pixel, which, is then processed to form a digital image.