Optics: Wave-Particle Duality of Light

The course is on physics for engineers, specifically on optics, which is the last chapter of the course.

Light is an electromagnetic wave and has both wave-like and particle-like properties, known as wave-particle duality.

Isaac Newton theorized that light is a stream of particles called corpuscles, but in 1665, evidence emerged that light has wave properties.

In 1887, Hertz showed that light is an electromagnetic wave, and later, experiments revealed that light is also a particle, with energy carried in discrete bundles called photons.

The wave model of light is used to study light propagation, while the particle model is used to study absorption and emission of light.

Optics is the branch of physics that studies the behavior and propagation of light.

The visible spectrum of light is a small part of the electromagnetic spectrum, ranging from 400 nanometers (violet) to 700 nanometers (red).

Beyond the visible spectrum, there are ultraviolet, X-rays, and gamma rays, which have higher energies and frequencies than visible light.

Infrared, microwave, and radio waves have lower energies and frequencies than visible light, and are invisible to the human eye.

Microwave radiation is harmful to living organisms, as it can cause water molecules to boil, leading to harm or death.

The wave-particle duality of light is reconciled in quantum electrodynamics, a higher physics subject.

The study of light can be represented using wavefronts, which describe the propagation of light, or rays, which represent the direction of travel of the wave.

The relationship between wavefronts and rays is that the rays are always perpendicular to the wavefronts.

Electric charges in accelerated motion, such as oscillating or accelerating charges, are the basic sources of light.

All bodies emit light, including humans, who emit infrared radiation, but only when alive.

Other sources of light include electric discharges through ionized gases, such as fluorescent lamps and stars, and lasers, which produce a narrow beam of radiation.

The speed of light in vacuum is approximately 3 x 10^8 meters per second, and is a universal constant.

One meter is defined as the distance light travels in 1/299,792,458 of a second.

One light year is approximately 9.46 trillion kilometers, and is a unit of distance, not time.