Introduction
Observing the interaction of atoms with various forms of radiant, or transmitted, energy, such as the energy associated with visible light that we detect with our eyes, infrared radiation that we feel as heat, ultraviolet light that causes sunburn, and x-rays that produce images of our teeth or bones, scientists discovered much of what we know about the structure of the atom. You should be familiar with all of these types of radiant energy. We begin our explanation of how our current atomic model came to be by outlining the properties of waves and the particle nature of electromagnetic radiation. Light as a Wave Light is a transverse electromagnetic wave that the average person can see. Experiments on diffraction and interference were the first to demonstrate the wave character of light. Light, like other electromagnetic waves, can traverse a vacuum. Polarisation can be used to highlight the transverse character of light. Light, according to Christian Huygens, travels in waves. Huygens was a contemporary of Isaac Newton. However, Isaac Newton believed that light was made up of particles too tiny to be detected individually. Thomas Young, an English physicist, experimented in 1801 that demonstrated that light acts like a wave. He used two thin, parallel slits to pass a light beam through.

When a ray of light approaches a smooth polished surface and the light ray bounces back, it is called the reflection of light. The incident light ray that land on the surface is reflected off the surface. The ray that bounces back is called the reflected ray. If a perpendicular were drawn on a reflecting surface, it would be called normal. The figure below shows the reflection of an incident beam on a plane mirror. Here, the angle of incidence and angle of reflection are with respect to normal and the reflective surface.

Refraction is an important term used in the Ray Optics branch of Physics. Refraction of light is defined as the change in direction or the bending of a wave passing from one medium to another due to the change in speed of the wave. Some natural phenomena occurring in nature where refraction of light takes place are the twinkling of stars, the formation of mirages and Rainbows, Optical illusions, and many more. The major cause of refraction to occur is the change in the speed of waves in different mediums, which is different due to the difference between the densities of the mediums. e.g. the speed of light in a vacuum is maximum. Snell’s Law provides a quantitative description of the amount of bending of a wave, that depends on the refractive index of the two mediums. Let’s learn more about refraction like the Laws of Refractions, Causes of Refraction, Types of Refraction, Examples, and Applications of Refractions in the article below.

Optics is a branch of Physics – it’s the science that deals with light. Optics explains how light energy behaves and interacts with matter. Some of the earliest recorded experiments in optics were done by ancient Egyptians, Mesopotamians, and Greeks using glass lenses and reflective materials like obsidian. During the Middle Ages and Enlightenment periods, the significant work of scientists Ibn al-Haythem (Book of Optics c1011) and Sir Isaac Newton (Opticks, 1704) made contributions to the field of optics with their observations of the visible spectrum and how light moves through different substances, as mentioned in Chapter 1.1 History of colour theories. Other significant developments, such as Galileo’s refracting telescope (c.1609), also had a great impact on the fields of optics and astronomy. Since that time, many technological developments have expanded the field of optics to include both the visible and non-visible spectrum.