Review on Handheld Durable Small Diffraction Spectroscope by Doris Tran

It's a bit small and doesn't have a scale, but it does the job. The picture shows the spectrum of a fluorescent lamp above my bed. I brought the spectroscope close to the tablet's camera lens to capture this image. Emission bands at 436, 487 and 546 nm due to mercury and terbium determined using Wikipedia. When you turn on a fluorescent lamp, the noisy electrons collide with the outer electrons of the mercury gas, causing them to jump to higher energy levels. As they fall back, they primarily emit ultraviolet photons, which are absorbed by rare earth elements such as terbium that coat the inner surface. These in turn are excited and emit visible photons.