Use a CD disk - really - it disperses light similarly to a dispersive prism. You can then see and estimate the amount of red, blue and green in a light. It works very well if you just want to check blue light sources at night. And you can even make a DIY spectrometer with it! https://youtu.be/p3MzQ1OF3lk
Use a CD disk - really - it disperses light similarly to a dispersive prism. You can then see and estimate the amount of red, blue and green in a light. It works very well if you just want to check blue light sources at night. And you can even make a DIY spectrometer with it! https://youtu.be/p3MzQ1OF3lk