This is from an advanced laboratory course for physics majors, in which I used several different LEDs to stimulate the photoelectric effect. Using data from this, I estimated the ratio of Plank's constant to the electron charge. The blue LED is special because its development resulted in the 2014 Nobel Prize in physics.
<a href="//commons.wikimedia.org/w/index.php?title=User:Michaelmcginnis9&amp;action=edit&amp;redlink=1" class="new" title="User:Michaelmcginnis9 (page does not exist)">Michael McGinnis</a>
CC BY 4.0
<span class="int-own-work" lang="en">Own work</span>