Because they go from trough to trough.
I said, "If I'm saying goodbye to someone I like it's usually a longer one."
It totally came out of the purple...
A 'hue' man.
and my teacher starts counting wavelengths to help us learn a concept. "One lambda, two lambda, three lambda" suddenly I chime in "man, I thought I was the only one trying to fall asleep here". My teacher looked at me obviously ready to scold me but before he does I proudly explain myself "Get it? Like counting sheep!". Believe me, the groan my classmates gave me was one for the ages.
The ceremony was dull, but the reception was great.
Bit of context: Mum and dad are visiting my house which I'm renovating. Today's job is to put on new doors. We are sitting watching TV and finish watching a few episodes.
I say, "ah well these doors aren't suicidal".
Mum gives a quizzical look.
Dad says, "yep they won't hang themselves."