Physics Photo of the Week

Warren Wilson College

Dec. 3, 2004

What is this?  Decide on your best answer before peeking at the answer.

  1. A manhole (personhole?) cover with an array of holes
  2. The inside of an airtrack
  3. A diffuser consisting of an array of holes to limit the airflow through an air duct
  4. The inside of an LED traffic light

Peek at the answer here after you have made your selection.

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to

Click here to see all Physics Photo of the Week for 2004.