2008 HS Photo Contest Pictures

2008 High School Physics Photo Contest Pictures

2008 AAPT High School Physics Photo Contest
Winner's Showcase

Click on image to resize

Honorable Mention - Natural

Title: Specular vs. Diffuse Reflection
Student: Jamie Bachmann
School: The Walker School, Marietta, GA
Teacher: Sandra Rhoades

Reflection of light on a surface depends on the texture of that surface. Light reflected on an uneven or granular surface undergoes diffuse reflection, while light reflected on a smooth, shiny surface experiences specular reflection. Specular reflection follows the law of reflection, which states that the angle of incidence is equal to the angle of reflection. Specular reflection produces mirror-like images. Diffuse reflection also follows the law of reflection. However, the angle of incidence and the angle of reflection are the angles to the normal. On a smooth surface, the normal line does not change, but on a rough surface it does. Therefore, on a rough surface, each angle of incidence is reflected at a different orientation, resulting in several different angles of reflection. This natural photo depicts a reflection of car rims on asphalt, an uneven surface. Since asphalt is granular, diffuse reflection would normally occur, reflecting the light in many directions. Interestingly though, the reflection produces a mirror-like image, as if reflected from a smooth surface. Because the photo was taken when the sun came out directly after rain, the asphalt was still wet. Water filled the uneven crevices of the pavement, creating a smooth surface. Therefore, when the sun hit the rims and reflected off of the wet pavement, specular reflection occurred and the angles of reflection were identical, producing the spiral image of the rim.


Back    Photo Contest Home    Next