# Speed of sound: Quiz

Question 1: In a real material, the stiffness of the springs is called the elastic modulus, and the mass corresponds to the ________.
CopperDensityGoldIron

Question 2: Just as light waves will refract towards a region of higher index, sound waves will ________ towards a region where their speed is reduced.
RefractionOpticsSnell's lawMetamaterial

Question 3: Each frequency component propagates at its own phase velocity, while the energy of the disturbance propagates at the ________.
MomentumWaveMatter waveGroup velocity

Question 4: See the section on gases in ________ for a more complete discussion of this phenomenon.
IronHydrogenOxygenSpecific heat capacity

Question 5: This figure for ________ (or any given gas) increases with gas temperature (equations are given below), but is much less dependent of pressure or density for a given gas.
EarthNatureAtmosphere of EarthHistory of the Earth

Question 6: In fact, assuming an ________, the speed of sound c depends on temperature only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out).
EntropyIdeal gasStatistical mechanicsMaxwellâ€“Boltzmann statistics

Question 7: But air does contain a small amount of CO2 which is a dispersive medium, and it introduces dispersion to air at ultrasonic frequencies (> 28 ________).
JouleVoltHertzPascal (unit)

Question 8: In the Earth's atmosphere, the most important factor affecting the speed of sound is the ________ (see Details below).
TemperatureThermodynamic temperatureLightningWater vapor

Question 9: Since temperature and thus the speed of sound normally decrease with increasing altitude, sound is ________ upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source.
Refractive indexMetamaterialOpticsRefraction

Question 10: Examples are ________, acoustic communication and acoustical oceanography.
Marine mammals and sonarSonarEcho soundingBioacoustics