Name ______ KEY ___________________________________ Date _________ Period ______
Unit 13: Sound and Light Review
v=fλ
1.
Each instrument has its own blend of harmonics, so the same note can sound
different.
What is the scale used to measure loudness?

6.
Pitch is a measure of the wave’s frequency. Humans hear from 20 – 20,000 Hz.
How can different instruments play the same note, yet sound different from each other?

5.
Sound cannot travel through a vacuum. The energy has to be transferred
between particles. Light does not need a medium.
What wave property does pitch relate to? In what range do humans generally hear sound?

4.
Sound is a longitudinal wave. It moves with a series of compressions and
rarefactions.
What does it mean that sound needs a medium? Does light need a medium?

3.
c = 3 x 108 m/s
What kind of wave is a sound wave? How does sound energy travel through air?

2.
v = 331 + 0.6 T
The decibel scale is used to measure loudness
Compare the sound of a 35 dB noise to that of a 55 dB noise in terms of:
a. Amplitude of the waves

The amplitude will be ten times higher for the 55 dB sound.
b. The perceived loudness to an observer.

7.
Which is faster: the speed of light or the speed of sound? What is the speed of each
around room temperature?

8.
The 55 dB sound will seem twice as loud to the observer.
The speed of light (3 x 108 m/s) is about 1,000,000 x faster than sound (about
340m/s).
What is the relationship between the speed of sound and:
a. Its medium?

The more packed the atoms are, the faster the sound travels (Ex: water is
faster than air)
b. Air pressure?

Higher pressure creates more collisions and therefore increases speed.
c. Temperature?

Higher temperature means higher speed
9.
What is the speed of sound at a temperature of 33.9 °C?
v = 331 + 0.6T = 331 + (0.6)(33.9 °C) = 351 m/s
10.
What is the difference between subsonic and supersonic flight? What happens when you
cross the sound barrier?

11.
Describe what happens when an ambulance drives past you with its siren on.

12.
Beats are oscillations that occur when sound waves are not the same pitch. When
waves are close, but not exactly the same, you will hear a beat.
What is the beat frequency between a 238 Hz tone and a 242 Hz tone?

17.
The open end of a pipe creates an antinode, while the closed end is the node of
the wave.
What are beats? When would you hear a beat?

16.
Frequency is inversely proportional to wavelength. Low frequency instruments
are larger so they can create the longer wavelengths needed.
What part of the wave occurs at the open end of a pipe? At the closed end?

15.
The Doppler affect is the apparent change of pitch from a sound source which is
moving to/from the observer.
Use the relationship between frequency and wavelength to explain why instruments that
produce low pitches are typically larger than those that produce high pitches.

14.
When an ambulance drives toward the observer, it pitch increases as it
approaches. When the ambulance passes and moves away, its pitch deceases.
What is the Doppler Effect? What are some uses of the Doppler Effect?

13.
Subsonic flight is below the speed of sound, while supersonic flight is faster than
the speed of sound. Breaking the sound barrier creates a sonic boom where loud
sound abruptly changes from silence.
The beat frequency between a 238 Hz tone and a 242 Hz tone would be 4 beats
per second.
How can sound waves interact with surfaces?

Sound waves can be reflected (reverberated or echo), refracted through surfaces,
diffracted through spaces, or absorbed by surfaces.
18.
What is light? How does it move from space?

19.
Why does a pencil in a cup of water look bent compared to the part above the water?

20.
Light intensity is known as brightness. Intensity follows the inverse-square law,
so it decreases by the square of the distance as you move from the source.
What are photoreceptors and what do they do? Which is responsible for color vision?
Which is more sensitive to light?

24.
The color of a wave is determined by its wavelength. Different colors of light
have different wavelengths (ex: red light has a longer wavelength than blue).
What do we call light intensity? How does light intensity change as you move away from
the source?

23.
Objects have certain wavelengths that they absorb and certain wavelengths that
are reflected. We see the reflected light waves as the color of the object.
What property of a wave determines color? What is different about different colors of
light?

22.
A pencil in a cup of water looks bent because the water refracts the light as it
passes through more than air does.
Why do we see colors on objects? What happens to the light waves we see and those we
don’t?

21.
Light is electromagnetic radiation that is visible to the human eye. Light moves
in a straight line from its source.
Photoreceptors are cells in the eye that detect light. Cones are responsible for
color vision (red, green, blue) and rods are more sensitive to light.
Differentiate between transparent, translucent, and opaque surfaces.

Transparent surfaces permit all light to pass through, translucent surfaces
scatter some light and may not show a complete image, and opaque surfaces do
not allow anly light to pass through.