cheap multispectral imaging

AZ 6-12 Science

PS4: Waves and Their Applications in Technologies for Information Transfer

This one has been a favorite of mine since I was about ten years old.  Physiology and anatomy of color vision leads us to the conclusion that color is an illusion of our retina and processing by our brains.  I was subbing at a middle school that was in the middle of a science assessment exam.  One of the messages was that the colors we see are based on reflected light.  Which color of t-shirt will heat up faster in sun light:  blue or yellow?  Blue is a cool color whereas yellow and red area warm colors.


“A wave model of light is useful for explaining brightness, color, and the frequency dependent bending of light at a surface between media (prisms). However, because
light can travel through space, it cannot be a matter wave, like sound or water waves.
 Appropriately designed technologies (e.g., radio, television, cell phones, and wired and wireless computer networks) make it possible to detect and interpret many types of signals that cannot be sensed directly. Designers of such devices must understand both the signal and its interactions with matter. Many modern
communication devices use digitized signals (sent as wave pulses) as a more reliable way to encode and transmit information.”

In this case dyes in the t-shirts absorb some wavelength of sunlight while reflecting others.  The wavelengths that are absorbed heat up the fabric.  The actual test was thankfully much simpler than the written requirement.



“The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing. The reflection, refraction, and transmission of waves at an
interface between two media can be modeled on the basis of
these properties.
Combining waves of different frequencies can make a wide variety of patterns and thereby encode and transmit information. Information can be digitized (e.g., a picture stored as the values of an array of pixels); in this form, it can be stored reliably in computer memory and sent over long distances as a series of wave pulses.
Resonance is a phenomenon in which waves add up in phase in a structure, growing in amplitude due to energy input near the natural vibration frequency. Structures have particular frequencies at which they resonate. This phenomenon  ….”

Kids in band probably are getting way more theory of sound and first hand experience of resonance than what is covered in physics class.  The RGB color scheme and perceived colors in printed images perhaps more biology than chemistry/physics addressed in color vision.


The color cube

This example was created with Paint,  Many of the color combinations in the videos produced by my hack “multi-spectral” imaging device are shades of pink light created by combinations of red, green, and blue LEDs from SuperBright LEDs.  When we go to Paint we can create many shades of pink by holding blue and red at about 90% saturation and adjusting the green saturation.


Note that saturation in Paint is 255.  This is why the equal combinations of red, green, and blue light are gray instead of pure white, the star on the left.

A red green and blue floral print t-shirt

The color of the white hemi-circular piece of plastic indicates the color of the incident light.  Note that the t-shirt also has some purple in it.

Here we have another floral print fabric in colors that are not close to the RGB color scheme.

This device has been a great toy that has taught me just how much I do not know.  While walking the dogs I found what appeared to be a white puff ball fungus.  White is white because it reflects all wavelengths of visible light, right?  The sky is blue because shorter wavelengths of light scatter more.   Our sunsets are red because when the sun gets close to the horizon, blue light is scattered out into space.  NASA has a few interesting things to say about the red sky on Mars.  This said, I was totally unprepared for what I found while walking the dogs.

Note that little holes in this object become visible with blue light.  What appears to be magenta light (blue plus red) becomes obviously two different colors when these colors are reflected on the surface of this object.

These are some images of a stick.  I’ve included an image taken with  a 10x dissecting microscope that stamp collectors light to use.

It should be noted that “white” LED light is really not an equal mixture of all wavelengths.  Scientists are making progress in that direction.  How our digital cameras mess up the color saturation of our photos is a separate rant hat the how and why of which will never be on a middle school science exam.

Here is an image of a yellow fall leaf.  “White” LED light is one of the options in the strip of SuperBright LED lights.

This one was taken in normal sunlight.


The follow up might be to extract compounds from these objects and resolve them with paper chromatography.









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