Chapter 42-Photoelectric effect

A picture is worth a 1000 words ! The stunning image below helps you keep this universal Effect in mind always.

The photoelectric effect reopened the debate among scientists , whether Light is a Particle or a Wave.

The story started with Isaac Newton describing Light as a particle in his Corpuscular Theory of Light, then Refraction and Diffraction phenomena were found later which indicated that Light should be a Wave.

However, when the Photoelectric Effect was discovered and explained by Einstein, it could be explained only if light behaves like a Particle. Einstein then came up with the Quantum Theory of Light, where each “particle” is thought of as a small packet of energy, called Quanta.

Thus, Light and Energy meant one and the same thing.

Following topics are covered:

1) Photon theory of light- about Photons

2) Photoelectric Effect, Planck’s constant, Work Function, Threshold Frequency

3) Tabular chart- Why Wave Theory fails to explain Photoelectric Effect

4) ENERGY of ligth beam –  FREQUENCY versus INTENSITY

5) Practical application of Photoelectric effect – Solar Panels

6) Planck constant

7) Work Function

•  what is eV , how is it a unit of energy of light quanta
• Work Function determines if electrons are ejected
• Cases 1 and 2 – with visible Light Beam

8) Threshold Frequency (threshold wavelength)

9) Solved problems