Properties of Waves Test Make-up

Scientists and engineers use graphs and mathematical values to model wave patterns. A group of students adjusted a wave tank to create waves as shown in this graph. Using data from the graph, which of the following statements best describes the amplitude of the waves they made?

• 1. The amplitude is 2, because it goes up to 1 and down to -1.

• 1. The amplitude is 1, because it goes up to 1 and down to -1.

• 1. The amplitude is 4, because it repeats starting at 0, 4, 8, 12, etc.

• 1. The amplitude is 2, because it crosses the x-axis at 0, 2, 4, 6, etc.

For a class assignment, a group of students were directed to create two different waves. There was a requirement: the two waves needed to share at least one property which was exactly the same, and at least one property which was different. After graphing their results, as shown below, they believed they had successfully completed the assignment. Based on the information provided in the graph the students were:

• 1. not successful, because the two waves do not have any properties that are the same.

• 1. not successful, because the two waves do not have any properties that are different.

• 1. successful, because the amplitudes are the same and the wavelengths are different.

• 1. successful, because the wavelengths are the same and the amplitudes are different.

The GPS, or Global Positioning System, uses waves from several different satellites to pinpoint a location on Earth. To do this, a GPS receiver must find the distance to at least four different satellites. Although not mechanical, the waves from satellites are modeled using the same properties. The receiver uses the mathematical properties of these waves to determine each distance.

If the number of wave cycles is known, what other wave property is sufficient (is enough) to calculate the distance that the signal of the wave travelled from a given satellite to the receiver?

• 1. the amplitude, by multiplying the amplitude by the number of wave cycles

• 1. the frequency, by multiplying the frequency by the number of wave cycles

• 1. the wave length, by multiplying the wave length by the number of wave cycles

• 1. the wave speed, by multiplying the wave speed by the number of wave cycles

Rebecca and Ari used a spring toy to produce the first wave shown in blue below. Then they shook the spring toy faster to create a second wave pattern with increased frequency, as shown in red. After looking at the data they realized the data showed changes that could not be explained by ONLY shaking the spring faster. Based on the information provided, which of the following statements best describes the cause of these results?

• 1. They shook the spring both faster and harder, as shown by the increase in wavelength.

• 1. They shook the spring both faster and harder, as shown by the increase in amplitude.

• 1. They shook the spring both faster and harder, as shown by the decrease in wavelength and the increase in amplitude.

• 1. They were mistaken about their claim, and the data can be explained by only shaking the spring faster.

A tuning fork, which produces a sound with 261.6 Hz, is struck and placed on a long slender gold

rod. The sound waves travel through both the air and through the gold. The speed of sound in gold is about 10 times faster than the speed of sound in air.

Based on the wave relationship “wave speed = frequency × wavelength”, which of the following

statements best describes the sound waves in each material?

• 1. The wavelength of the sound in the gold will be about 10 times longer than the wavelength in the air.

• 1. The wavelength of the sound in the air will be about 10 times longer than the wavelength in the gold.

• 1. The frequency of the sound in the gold will be about 10 times greater than the wavelength in the air.

• 1. The frequency of the sound in the air will be about 10 times greater than the wavelength in the gold.

AM and FM radio stations use different technologies, but both transmit signals using radio waves. Radio waves are not mechanical waves, but are modeled using the same mathematical features. AM stands for amplitude modulation, and operates by changing the amplitude of the signal wave for different sounds. FM stands for frequency modulation and makes variations in the signal waves frequency for different sounds. Below are two diagrams showing wave patterns. Based on the diagrams and the properties of wave patterns, which statement best states the difference between AM and FM signals?

• 1. Figure 1 shows FM and Figure 2 shows AM.

• 1. Figure 1 shows AM and Figure 2 shows FM.

• 1. Figure 1 shows a combination of AM and FM.

• 1. Figure 2 shows a combination of AM and FM.

Investigation A

You have been hired by TCI, the publisher of this text book, to be in charge of a team to build a machine to make wave patterns for classrooms. This machine will help teachers demonstrate the wave relationship between a wave’s speed, frequency and wavelength. The materials you have are a long-coiled spring and a motorized device which sends a pulse pattern down the spring. You are able to control this motorized device by setting the frequency and by changing the distance it moves back and forth when making the pulse.

Your first task is to provide directions about changing the wave speed. Which of the following statements correctly states the requirements to increase the wave speed?

• 1. Increasing the frequency will increase the wave speed.

• 1. Increasing the tension in the spring will increase the wave speed.

• 1. Increasing the distance of the back and forth motion will increase the wave speed.

• 1. Increasing both the frequency and the back and forth distance will be needed to increase the wave speed.

Investigation A

You have been hired by TCI, the publisher of this text book, to be in charge of a team to build a machine to make wave patterns for classrooms. This machine will help teachers demonstrate the wave relationship between a wave’s speed, frequency and wavelength. The materials you have are a long-coiled spring and a motorized device which sends a pulse pattern down the spring. You are able to control this motorized device by setting the frequency and by changing the distance it moves back and forth when making the pulse.

Based on the wave relationship “wave speed = frequency × wavelength”, what settings could you use to make waves with a 2 m wavelength?

• 1. Wave speed at 2 m/s with a frequency of 2 waves per second.

• 1. Wave speed at 2 m/s with a frequency of 4 waves per second.

• 1. Wave speed at 4 m/s with a frequency of 2 waves per second.

• 1. Wave speed at 4 m/s with a frequency of 4 waves per second.

Investigation A

You have been hired by TCI, the publisher of this text book, to be in charge of a team to build a machine to make wave patterns for classrooms. This machine will help teachers demonstrate the wave relationship between a wave’s speed, frequency and wavelength. The materials you have are a long-coiled spring and a motorized device which sends a pulse pattern down the spring. You are able to control this motorized device by setting the frequency and by changing the distance it moves back and forth when making the pulse.

You have asked your team members to suggest improvements to make the wave machine cheaper to build and easier to use. Which of the following statements about design changes is true?

• 1. The frequency adjustment is not necessary.

• 1. The spring tension adjustment is not necessary.

• 1. The back and forth distance adjustment is not necessary.

• 1. All the current adjustments are necessary to demonstrate the wave relationship.

Investigation B

When sound waves are produced with different frequencies they are heard as different pitches, or notes. When a wave’s frequency is halved or doubled it produces a similar sounding note, and we use the same letter to identify both notes. The two notes are said to be an octave apart. Notice that the wavelength is shorter for higher frequency waves and longer for lower frequency waves. The wavelength of a note changed by exactly one octave is half as long or twice as long as the other note. Note: Many instruments are tuned using the A 440 note just above middle C on the piano.

Based on the data provided, what would be the frequency of the A note in the next higher octave above the tuning reference note?

• 1. 110 Hz

• 1. 220 Hz

• 1. 440 Hz

• 1. 880 Hz