Science Buddies: "Ask an Expert"

6th grade student doing project on stealth technology on your website under physics. This suggests conducting experiment by measuring scatter/reflecion of light from an LED flashlight wiht a lux meter from inside a black cardboard box on various 3D shapes (cylinder, V-shape, W-shape, etc). Teacher recommended doing this with a laser light instead.

The light from the LED flashlight will reflect off most or all of the 3D object and the amount of light reflected back to hee lux meter will vary depending on the shape/angles of the 3D objects. If we use a laser pointer instead which has a very narrowly focused beam and will only hit a small portoin of the 3D object, will we really be able to detect any variation in the amoun tof light reflected back as the light may not "touch" any of the angles and all will appear to be similar "flat" object? We will be using an inexpensive lux meter (less than $30) for this measurement.

g8rdotony wrote:Teacher recommended doing this with a laser light instead.

The recommendations in most Science Buddies projects are usually well thought out; however, there have been some notable exceptions. In this case, my personal experience has been that light from an LED flashlight is incoherent light with several distinct discrete wavelengths and simple incident light meters provide fairly accurate measurements of this kind of a light source intensity and reflections and refractions thereof.

So now you have a scientific dilema of which expert to believe, your teacher or the Science Buddy author. This means you have an opportunity to run an experiement to prove which light source works best at detecting the stealth nature (or lack there of) for different object shapes. I recommend you do the same experiments twice, one with the Science Buddies recommended light source and one with your Teacher's recommended light source.

Do some reading on diffraction and think about how that might be involved in scattering of light to form a hypothesis on which light source might make it easier to detect an object by measuring reflected light with an incident light meter.