A student uses a ripple tank to project a wave pattern onto a blank sheet of paper on the floor beneath the tank. Using a standard ruler, they measure the distance between consecutive bright bands on the paper to estimate the wavelength, and use this to calculate a wave speed of 42 cm/s.
Which of these is the primary reason why this speed estimate is incorrect?
The ruler used did not have millimeter divisions.
The light rays diverge, causing the projected wave pattern on the screen to be magnified.
The student did not measure the depth of the water in the tank.
The frequency of the wave generator was fluctuating during the measurement.