University:
Texas A&M University
Course:
PHYS 201 | College Physics
Academic year:

2019
Views:

227

Pages:

2
Author:

Dixie Summers

Light PPT Outline Basic Properties • Light travels in straight “beams” • beams = the length, height, and width of light Basic Properties • Light travels much faster than sound • Speed of light = 983,571,056 feet per second! • Speed of sound = 1087 feet per second • Example: we see the explosion from a gunshot, then we hear the bang. Basic Properties • Shadows are formed when light is blocked by an object • Examples: shadow hand puppets, shade from a tree, etc • Basic Properties • We see things because light beams reflect into our eyes Light Interactions: Refraction • Refraction occurs when light is bent through interactions with another medium • This is due to a change in speed • Examples: straw in a water glass, prisms, etc Light Interactions: Reflection • Occurs when light bounces evenly off an object at equal angles • Examples: mirrors, smooth water surfaces, glass windows Reflection: Convex Mirrors • Reflective surface that curves outward and is thicker in the center than on the edges • Light rays converge (are brought together) • Image is upright, and reduced (smaller than the real object) • Examples: Corner mirrors in stores, rearview mirrors, etc Reflection: Concave Mirrors • Concave mirrors have a reflective surface that curves inward • Images in mirror appear upside down and smaller at further distances • If closer to the mirror, images flip right-side up and appear larger Light Interactions: Scattering • When light hits a rough surface, the reflection of the image bounces off at different angles and scattering of the light occurs • This is also called diffuse refraction Light Interactions: Absorption • When light strikes an object it not only reflects the light (the colors you see) but it also absorbs the light (the colors you don’t see) • Example: blue jeans absorb all the colors of light except blue, which is the color reflected Light Interactions: Absorption • White is the presence of all colors • No color is absorbed, all colors are reflected • Black is the absence of all colors • All color is absorbed, no color/light is reflected. Absorption: Secondary Colors • If the color you see is a secondary color (orange, green, purple) then it reflects a combination of the primary colors. • Example: purple objects absorb orange, yellow, and green light, but they reflect red, blue, and purple light. Absorption: Filters • Filters can be used to “block out” or cancel different colors of light • In regular lighting, red and blue are reflected • In a red light filter, the shirt would continue to appear red, but the jeans would look black • In a blue light filter, the jeans would look blue, but the shirt would appear black. Transparent • Light is able to travel through an object • No scattering occurs • Examples: clear windows, eyeglasses, plastic wrap, etc. Translucent • Some light is able to pass through an object but not all, and a light shadow is cast • Objects you can partially see through • Some light scattering occurs • Examples: Tissue paper, tinted windows, clouds, etc. Opaque • Light is blocked by an object and a dark shadow is cast • Cardboard, eyelids, aluminum foil, wooden door, etc.