7 – JAENA (SPJ)
* Light is part of the electromagnetic spectrum, the spectrum is the collection of all waves, which include visible light, Microwaves, radio waves ( AM, FM, SW ), X-Rays, and Gamma Rays.
* In the late 1600s, important questions were raised, asking if light is made up of particles, or is it waves .? * Sir Isaac Newton, held the theory that light was made up of tiny particles. In 1678, Dutch physicist, Christian Huygens, believed that light was made up of waves vibrating up and down perpendicular to the direction of the light travels, and therefore formulated a way of visualising wave propagation. * This became known as 'Huygens' Principle'. Huygens theory was the successful theory of light wave motion in three dimensions. Huygen, suggested that light wave peaks form surfaces like the layers of an onion. In a vacuum, or other uniform mediums, the light waves are spherical, and these wave surfaces advance or spread out as they travel at the speed of light. * In 1803, Thomas Young studied the interference of light waves by shining light through a screen with two slits equally separated, the light emerging from the two slits, spread out according to Huygen's principle. Eventually the two wave fronts will overlap with each other, if a screen was placed at the point of the overlapping waves, you would see the production of light and dark areas * Later in 1815, Augustin Fresnel supported Young's experiments with mathematical calculations. * In 1900 Max Planck proposed the existence of a light quantum, a finite packet of energy which depends on the frequency and velocity of the radiation. * In 1905 Albert Einstein had proposed a solution to the problem of observations made on the behaviour of light having characteristics of both wave and particle theory. From work of Plank on emission of light from hot bodies, Einstein suggested that light is composed of tiny particles called...