1. The problem statement, all variables and given/known data Say we are observing plane wave patterns on table. The depth of water is the same everywhere in ripple tank. The frequency of waves is 12 Hz and wave length is L (lamda). We see the wave pattern as stationer while looking at wave pattern through the slots of stroboscope which turning at 2 Hz frequency. What is the number of slits if we measure the distance between two wave crest as L/3? (A: 18) 2. Relevant equations Fw = n Fs Fw: Wave freq Fs: Strobe freq n: Number of slots 3. The attempt at a solution I could not solve this problem. I can not imagine stationer waves which has smaller wave length. Is it possible to see the waves as stationer while slot frequency is bigger then wave frequeny?