Photocatalysis
The up and down pattern is how we show light. The high points are called crests and the low are called troughs.  Light has three characteristics that we use to describe it.  Wavelength (λ) is the distance between two peaks that are next to each other. Frequency (ν) is the number of times a unit of light can pass by a point over time. Amplitude is the vertical distance between a peak and the next trough.