PHOTOELECTRIC EFFECT

Source: Hindu

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Context

Researchers at institutions like SLAC National Accelerator Laboratory have discovered photoemission delays in X-ray regimes.

Details

About the research

• Researchers found that in nitric oxide molecules, core electrons were found to be ejected with a delay of up to 700 attoseconds compared to nitrogen electrons.
• These delays help to understand electron correlation (one electron's movement affects others).
• This helps in designing molecules with specific properties, such as better conductors or insulators.
• This could lead to the development of materials with custom-designed electronic properties.

Trivia:

X-rays are a kind of electromagnetic radiation. This is typically produced within a vacuum tube where a high voltage excites the electrons released by a hot cathode. This radiation has enough energy to shift electrons from atoms to produce observable ions. When X-rays strike an object, some X-rays will be absorbed and some reflected, depending on the density of the object. Those that are reflected can be captured as an image on a photographic plate or detector.

 

About Photoelectric Effect

Source: Sciencefacts

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• It is a phenomenon where electrons are ejected from a material when it absorbs electromagnetic radiation, such as light.
• This effect played a pivotal role in establishing quantum theory.
• The photoelectric effect helped prove that light has both particle and wave properties, leading to the concept of wave-particle duality.

 Background

• The photoelectric effect was first observed by Heinrich Hertzin 1887.
• In 1905, Einstein provided a theoretical explanation for the photoelectric effect (light could be quantized into photons). For this, he won the Nobel Prize in Physics in 1921.

Laws of Photoelectric Emission

• Emission of electronsonly occurs when the frequency of the incident light is above the threshold frequency.
• Number of electrons emittedis directly proportional to the intensity of the incident light, provided the light's frequency is above the threshold frequency.
• Energy of the emitted electronsdepends on the frequency of the light, not its intensity.
• The emission of electronsis immediate and has no time lag once the appropriate frequency light is applied.

Trivia:

Robert Millikan conducted a detailed experiment in 1916 to verify Einstein’s equation for the photoelectric effect, which confirmed the relationship between photon energy and frequency.

Applications

• Photoelectric Cells (Photodetectors):Devices that convert light into electrical energy, used in light meters, solar panels, and automatic doors.
• Photomultipliers:Instruments used in scientific research to detect and amplify light signals.
• Solar Panels:Utilize the photoelectric effect to convert sunlight into electricity.
• Night Vision Devices:These use the photoelectric effect to amplify low-light images.

Sources:TheHindu

PRACTICE QUESTION Q: The photoelectric effect is not just a fundamental phenomenon in quantum physics but also has significant real-world applications. Discuss. (250 Words)