The colors of light

Summer term always feels like the term to experiment with experiments, to try variations in the curriculum. Rather than start with the Limits of Light, which is a day one activity during the regular term, I planned to start with the CD spectrograph boxes and then run Limits of Light, rather than the other way around. Experience the reality first, then the theory. 

The interesting twist was that due to a local high school graduation, there were no students for the morning session. By the time of the laboratory session two students had arrived on campus. 

The afternoon lab ran without the precursor video playlist on color. This is part of an attempt to reduce the number of videos as the tail end of the course is becoming too video heavy. The course has a core intent of being focused on science as the result of explorations that can be experienced.

CD spectrograph

What one sees with the human eye is different than what a digital camera can capture. In the above image the cyan band is more prominent than seen with the eye. The human eye sees a significant violet band to the left of the blue which is almost completely missing in this image. 

The morning session would be a wash out due to the graduation of the largest high school on island. Limits of Light was assigned as a home viewing option. 

Two students attended lab.

The introduction to the laboratory, which began with the CD spectrum box and then moved on to the microscope. Followed by the explanation to how we perceive light and the issue that we can never know if my yellow is your yellow. 

Both of the two students worked the Desmos based color exploration on their cell phones.

Set up Desmos starting with a color command. The color commands are case sensitive and use lowercase. Set up a function that can be set to the color chosen. Use the Edit List gear to assign the custom color to the function.

The shape will start off in the default color.

The custom colors will appear below the default color palette.

Editing the color command numbers will change the color of the function automatically.

Changing only c₁ updates the color of the function. 

The rgb function takes values from 0 to 255.

The HSV function is also entered in lowercase. The hue angle is a value from 0 to 360. The saturation is 0 to 1. The value is also 0 to 1 where the value is the brightness of the color. For those accustomed to luminosity in the HSL system, a luminosity of 50% is equivalent to a brightness value of 1 in HSV. Luminosities higher than 0.5 require reduction of the saturation in the HSV system. This make white a non-obvious color in HSV. White is hsv(0,0,1). Zero saturation and full brightness. 

Some diagrams put 0° at the top of the circle and then lay out the hues in clockwise order. This is the order often seen in diagrams for hue in Cascading Style Sheets. Desmos takes a trigonometric approach and puts 0° on the positive x-axis and then lays out the hues counterclockwise.