Week 3

• Light is a part of the electroagnetic spectrum that can be detected by the human eye.
• A Ray is the direction of the path taken by light.
• A beam ks a stream of light energy.
• Luminous sources are objects that make their own light.
• Non-luminous objects are objects that reflect light from the luminous sources.
• The incident ray is the ray of light approaching the mirror.
• The reflected ray is the ray of light leaving the mirror.
• The normal is a line that can be drawn perpendicular to the surface of the mirror.
• The normal line divides the angle between the incident ray and the reflected ray into two equal angles.
• The angle of incidence is the angle between the incident ray and the normal.
• The angle of reflection is the angle between the reflected ray and the normal.
• First law of reflection: the reflected ray and the normal drawn at the point of incidence all lie in the same plane.
• Second law of reflection: The angle of incidence is equal to the angle of reflection. (i=r).
• Refraction is the bending of a wave when it passes from one medium to another. The bending is causes due to the differences in density between the two substances.
• Law of refraction: The incident ray, refracted ray, and the normal to the interface of two media at the point of incidence all lie on the same plane.
• Law of refraction: The ratio of the sine of the angle incidence to the sine of the angle of refraction is a constant. This is also known as Snell's law of refraction.
• A photon is the smallest discrete amount or quantum of electromagnetic radiation. It is the basic unit of all light.
• Photons are always in motion and, in a vacuum, travel at a constant speed to all observers of 2.99 x 10^8 m/s. Commonly referred to as the speed of light.
• The theory that states that light behaves both like a wave and a particle is called the wave-particle duality theory.
• Non only is light made up of photons, but all electromagnetic energy is made up of photons.
• Photons are always electrically neutral, they have no electrical charge.
• The original concept of photon was developed by Einstein, however it was Lewis who first used the word photon to describe it.
• The shorter the wavelength the more energy. UV waves are shorter than visible light waves, so UV possesses more energy than regular light waves.