UPSC NDA I 2019 General Ability Solved Paper

Concept:The photoelectric effect is the emission of electrons from a metal surface when light of sufficient frequency falls on it.Explanation:Albert Einstein explained the photoelectric effect using the idea that light consists of discrete packets of energy called photons.Each photon transfers its entire energy to an electron in the metal.If the photon’s energy ($h\nu$) exceeds the work function ($\phi$) of the metal, an electron is emitted.Einstein’s equation: $K_\text{max} = h\nu - \phi$.He was awarded the Nobel Prize in Physics in 1921 for this discovery.The photoelectric effect also established the particle nature of light and led to the concept of wave–particle duality.Max Planck introduced the quantum of energy (Nobel 1918) but did not explain the photoelectric effect.Niels Bohr worked on atomic structure and quantum theory (Nobel 1922).Ernest Rutherford split the atom and proposed the nuclear model (Nobel 1908).Only Einstein provided the correct explanation for the photoelectric effect.Answer:Albert Einstein