• Lenses and mirrors affect light in multiple ways.300mm mirror lens - high key front image by pdtnc from Fotolia.com
  
  Light is essentially defined as the range of electromagnetic radiation that can be detected by the human eye. The electromagnetic radiation is composed of energized particles called photons that travel approximately 186,000 miles per second. Light travels in a straight line unless something causes it to alter its course. Mirrors and lenses are used in a variety of ways to affect light properties for scientific purposes.
  
  

Reflection

• Reflection is caused by light waves bouncing off of an object. Everything reflects some light since it is light reflection off of an object into the human eye that allows animals to see objects in front of them and differentiate color. Mirrors are shiny, opaque materials that light cannot penetrate. As a result, light bounces off of a mirror at the same angle that it struck the mirror, much like a pool ball bouncing off the bumper of a pool table. Mirrors are shiny enough that the light reflection causes an image as the light bounces off the surface of the mirror and then makes contact with lens in the eye.
  
  

Refraction

• Refraction occurs when a light wave's speed is altered as it passes through a new material. For example, a light wave's speed is slowed slightly through water compared to when it travels through air. This causes the wavelength of the light to shorten while the frequency remains the same, much like multiple train cars mushing together if the lead car suddenly stopped or slowed down dramatically in a short period of time. You can witness this by placing a pencil into a glass of water. It will appear that there is a bend in the pencil from the point where it enters the water compared with the part that sticks out of the glass. The lenses in the human eye can deteriorate, and the resulting refraction can make items blurry. Glasses and contacts accommodate this by altering the refraction so items can be seen clearly again.
  
  

Magnification

• Reflection and refraction can be used in combination to create an enlarged image of an object that is actually far away. Objects appear to be smaller at greater distances, but devices like telescopes and magnifying glasses use lenses and mirrors to focus the light that is reflecting off of a far away object and focus it onto a visual plane where the eye can see it. The eye then sees the object as larger and in greater detail than it can by itself at great distance.