A photograph shows six consecutive crests along the direction of travel. The distance from the first crest to the sixth crest is 30 cm. The frequency is 5.0 Hz. What is the wave speed?
0.06 m/s0.06\ \mathrm{m/s}0.06 m/s
0.25 m/s0.25\ \mathrm{m/s}0.25 m/s
1.50 m/s1.50\ \mathrm{m/s}1.50 m/s
0.30 m/s0.30\ \mathrm{m/s}0.30 m/s