Introduction to Wave Optics

Study Notes

Wave theory of light was proposed by Christiaan Huygens in 1678.
Corpuscular model of light was proposed by René Descartes in 1637 and further developed by Isaac Newton.
The wave model predicts that light travels slower in a denser medium, while the corpuscular model predicts the opposite.
The experiment by Foucault in 1850 proved that light travels slower in water than air, supporting the wave model.
Thomas Young's interference experiment in 1801 firmly established the wave nature of light.
The wavelength of visible light is extremely small, typically around 0.6 mm for yellow light.
Geometrical optics is a branch of optics where wavelength is considered negligible, and light travels in straight lines.
Maxwell's electromagnetic theory explained how light waves can propagate through vacuum.

Maxwell's equations describe the laws of electricity and magnetism.
By solving Maxwell's equations, he derived the wave equation which predicted the existence of electromagnetic waves.
Maxwell calculated the speed of electromagnetic waves in free space and found it to be very close to the measured speed of light.
This led to the conclusion that light is an electromagnetic wave.
Electromagnetic waves are composed of changing electric and magnetic fields.
These fields propagate through vacuum as light.

Superposition principle states that the resultant displacement at a point due to multiple waves is the vector sum of the individual displacements.
Interference is a phenomenon where two or more waves interact and produce a resultant wave with a different amplitude.
Constructive interference occurs when the waves are in phase, resulting in a larger amplitude.
Destructive interference occurs when the waves are out of phase, resulting in a smaller amplitude.
Young's double slit experiment demonstrates interference.

Diffraction is the spreading of waves as they pass through a narrow opening or around an obstacle.
Huygens-Fresnel principle combines Huygens' principle with the concept of interference.
Diffraction patterns are observed due to superposition of diffracted wavelets.

Polarization refers to the direction of oscillations of the electric field in an electromagnetic wave.
Unpolarized light has randomly oriented oscillations.
Polarized light has oscillations aligned in a specific direction.
Polarizers are materials that allow only light polarized in a specific direction to pass through.
Malus' law describes the intensity of light transmitted through a polarizer as a function of the angle between the polarizer's axis and the polarization direction of the incident light.