Category Archives: Photometry

Inverse Square Demo

Demo: OP-B-IS
Pira Index: 6B 10.15

 Lab Equipment  Directions
  1.  inverse square model
This is an important principle in photometry and in the sutdy of gravitational, electrical, and magnetic fields.
  1.  Level one shows the first distance from the origin, therefore 1^2 = 1 square area.
  2. Level two is two times the distance of level 1 from the origin, therefore 2^2 = 4 squares of area.
  3. Level three is three times the distance of level 1 from the origin, therefore 3^2 = 9 squares of area.
  4. After showing the above, note that intensity (of the origin’s energy) diminishes by the inverse of distance squared.


Blackbody Radiaton of Steel

Demo: OP-B-BR
Pira Index: 6B 40.50

 Lab Equipment  Directions
  1.  Sony video camera attached to stand (2 poles and 2 parallel clamps)
  2. telescope clamp
  3. monitor on a crate
  4. vice with nail
  5. propane torch
  6. 4 bungee cords (2 short, 2 long)
  7. BNC-RCA cable
  8. BNC-f to UHF-m adapter
  9. black cardboard screen supported by 2 cement bricks
  1.  Set up as shown with crate, monitor and vice bungeed to the cart. Turn on camera and monitor. (camera should be set to “night shot” and display should be off)
  2. Heat nail with torch until it glows red.
  3. As the nail cools and no longer glows, notice that the video camera will continue to pick up the infrared wavelengths.


Blackbody Boxes

Demo: OP-B-BB
Pira Index: 6B 40.20

 Lab Equipment  Directions
  1. 2 black index boxes with a hole in end
  1. Have students look at the hole in the end of the box. Which looks blacker, the box or the hole?
  2. Do you see any significant different in the blackness of the holes in the two boxes? Open the boxes to show that one box is white on the inside (the other is black).