Write your name, section, and today's date in the cell below:¶

Name - Section - Date -

Introduction¶

This lab will explore wave phenomena using a ripple tank setup.

Procedure: Calibration and setup¶

The ripple tank is already largely setup, but it requires some calibration and to be filled with water. In my experience, this is the simplest order in which to perform these steps:

1) Pour ~800 mL into the tank. 2) Measure the depth of the water at the corners, and raise and/or lower the three legs until the water is level. 3) Turn the knob that raises the front end of the wave generator until the center of the front bar barely touches the water. 4) Turn the knob in that adjusts the left/right balance until both sides are barely touching the water.

For this lab, you will measure various quantities using the projection screen (light shines from the lamp through the water, bounces off the mirror, and then can be seen on the screen). The dimensions of the projection on the screen are not the same as the dimensions of the pool and waves themselves, as the light from the lamp spreads out as it travels (i.e. the dimensions on the screen are larger than in the pool itself). For the first step, the goal is to measure the relation between the dimensions on the screen and the pool.

5) There are different ways to do this, but the simplest way is to place the two of the transparent yellow pieces in the water, such that each one can be seen on the projection screen, touching the edge of the projection screen. Then, measure horizontal width of the screen and the distance between the yellow pieces in the water. What is the projection factor $p=width(water)/width(screen)$ ?

Give answer here

Procedure: Wave speed¶

Turn the frequency to ~20 Hz and the amplitude to ~half the max value, and use the "constant" setting of the lamp. Use a timer to measure the time it takes one wave to travel from one end of the screen to the other. What is the wave speed (using the projection factor, the time, and the width of the screen)? - Give answer here (time and speed) Turn the frequency to $\sim$ 20 Hz and the light to strobe. Now, measure the wavelength directly on the projection screen. Frequency ( $f$ ), wavelength ( $\lambda$ ), and speed ( $v$ ) can be related by $f\lambda=v$ . Given this relation, the measured wavelength, and the given frequency on the wave generator, what is the wave speed (as before, convert the measured wavelength on the screen to the actual wavelength, using the projection factor). What are the measured wavelength and speed? - Give answer here (wavelength and speed) Increase the amplitude of the wave generator to ~3/4 of the max value, and repeat the above (both using the direct time measurement and using the wavelength measurement). - Give answer here (time and speed for the time-based measurement, wavelength and speed for the wavelength-based measurement) How does the wave speed depend on the amplitude of the waves? - Give answer here

Procedure: "Experiment 1"¶

The remaining parts of this lab are an adaptation of the example experiments given in the manual for the ripple tank. In particular, we are adapting experiments 1 and 2, so check the manual here for more info about the configurations of the different pieces.

Place the straight barrier at an angle in the tank, as shown in Experiment 1 Part 1. Measure the angle of incidence and the angle of reflection. There are two ways to do this, either by measuring the angles directly on the screen with a protractor (with the light set to strobe) or by taking a picture of the screen (with the light set to constant) and measuring the angles on the image with a digital protractor. Finally, repeat the process when the barrier is at a different angle.

Give indicence and reflection angles for the two different barrier angles. Replace the straight barrier with the curved barrier (oriented as shown in the Pasco manual, with the center of the circle pointed toward the wave generator). Measure the distance from the center of the curved barrier to the point where the waves converge, and measure the distance to the center of the circle formed by the curved barrier (either measuring using a ruler and compass on the screen or taking a picture and measuring them on your computer). What is the relation between the point where the waves converge and the center of the circle?
Give answer here (distance to circle's center divided by distance to point where waves converge)

Procedure: Experiment 2¶

Place the trapezoid in the water, as shown in the manual for Experiment 2 Part 1. The water should pass slightly above the trapezoid; if the water isn't deep enough, add water. Turn on the wave generator. Do the waves travel faster or slower (or at the same speed) when traveling over the trapezoid (i.e. do the waves travel faster or slower in shallower water)? - Give answer here Does the waves that pass over the trapezoid tend to converge or diverge? - Give answer here Now, replace the trapezoid with the curved piece, as shown in Experiment 2 Part 2. Does the round piece cause waves to converge or diverge? - Give answer here Now, flip the round piece so that the curved side faces the wave generator. Does the round piece cause the waves to converge or diverge?