Optics By Mr. Arhelo Caribbean Maritime Institute ADISOM, Year One. Enginneering Physics.
Review of Last Class
Light as a Wave Light is an electromagnetic wave. As light travels through space an electric field and a magnetic field oscillate perpendicular to the wave direction and perpendicular to each other. A light wave is transverse rather than longitudinal, since each field oscillates in a plane perpendicular to the direction of the wave. Unlike a pulse traveling down a length of rope, nothing is physically moving in a light wave. Light requires no medium! It can travel through space that contains matter (such as air, glass, or water) or through a vacuum.
Light as a Wave If light did need a medium in order to propagate, the earth would spend its days submerged in darkness and the sun would not be visible.
Properties of Light Light travels in straight lines: Laser
Properties of Light Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.
Properties of Light Light travels much faster than sound. For example: Thunder and lightning start at the same time, but we will see the lightning first.
Properties of Light We see things because they reflect light into our eyes: NoteBook
Reflection Of Light Most things we see are thanks to reflections, since most objects don’t produce their own visible light. Much of the light incident on an object is absorbed but some is reflected. the wavelengths of the reflected light determine the colors we see. When white light hits an apple, for instance, primarily red wavelengths are reflected, while much of the others are absorbed. A ray of light heading towards an object is called an incident ray . If it reflects off the object, it is called a reflected ray . A perpendicular line drawn at any point on a surface is called a normal (just like with normal force). The angle between the incident ray and normal is called the angle of incidence , i , and the angle between the reflected ray and the normal ray is called the angle of reflection , r .
Law Of Reflection A reflected ray lies in the plane of incidence and has an angle of reflection equal to the angle of incidence (both relative to the normal). θ i = θ r
Law of Reflection i r i = r Normal line (perpendicular to surface) incident r ays reflected rays
Reflection Of Light ▪ There are two types of reflection; but not all reflections form images. NOTE: Without reflection, we would only be able to see luminous objects like the sun, light bulbs and computer screens.
Diffuse Reflection Diffuse reflection is when light bounces off a non-smooth surface. This explains how we can see objects even when it seems the light shining upon it should not reflect in the direction of our eyes. It also helps to explain glare on wet roads: Water fills in and smoothes out the rough road surface so that the road becomes more like a mirror.
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- Fall '16
- Light, Total internal reflection, Geometrical optics