Controlling Variables
Some test questions ask which variables must be controlled in an experiment. It helps to start by writing an equation for the variables you are given. For the question below, write an equation that includes wavelength and frequency.
This equation gives you one variable to control: the wave speed. Next, think of any conditions that might affect this variable. You know that wave speed changes in a different medium, so the medium must be controlled. Other conditions that are often controlled include conditions in the lab, such as temperature and pressure, or quantities of matter, such as mass or volume.
Which variables must be held constant in an experiment to determine how the frequency of a sound wave affects wavelength?
time
wave speed
temperature
I only
II only
I and II only
II and III only
I, II, and III
(Answer: D)
Choose the letter that best answers the question or completes the statement.
Which of the following is required to transmit energy using mechanical waves?
medium
crest
trough
reflection
period
How are wavelength and frequency related for a wave moving at constant speed?
Wavelength equals frequency.
Wavelength is greater than frequency.
Frequency is greater than wavelength.
Wavelength is proportional to frequency.
Wavelength is inversely proportional to frequency.
Which of the following statements is generally true for the musical instrument (panpipes) below?
The longest pipe has the highest pitch.
The shortest pipe has the highest pitch.
The pipe in the middle has the highest pitch.
The pitch cannot be changed.
Any of the pipes could produce the highest pitch.
Which conditions best describe what happens when a transverse wave is reflected?
Some of a wave does not pass through a boundary or surface.
A wave enters a new medium at an angle.
A wave becomes longitudinal.
A wave combines with another wave.
A wave interferes with another wave.
Which of the following variables can affect the wavelength of a sound wave?
the medium
the frequency of the wave
the amplitude of the wave
I only
II only
I and II only
II and III only
I, II, and III
Ocean waves flow past a concrete support for a bridge. The support is 30 meters wide and it sits in very deep water. Which of the following is LEAST likely to occur?
The waves will reflect.
The waves will diffract.
The waves will lose some energy.
The waves will continue past the support.
The waves will refract.