Answers to Waves Review Packet
1. Draw a wave with a very high frequency and a very low frequency.
high frequency
low frequency
2. High frequency waves have shorter wavelengths while low
frequency waves have longer wavelengths.
crest
crest
crest
Amplitude = 1.7 cm
Amplitude
Wavelength (λ)
λ = 3.1 cm
trough
trough
If the image shows 6 seconds, what is the frequency of the wave?
f = number of cycles ÷ time
so f = 3 cycles ÷ 6 seconds
Therefore f = 0.5 cycles/second which means f = 0.5 Hz
trough
Compare and Contrast Longitudinal and
Transverse Waves
Longitudinal
Particles move
in the same
direction as
the direction
of the wave
Transverse
Both are
disturbances
that carry
energy
Particles move
at right angles
to the
direction of
the wave
5. When fans do “The Wave” at a football stadium, are they making a
transverse or longitudinal wave?
How do you know? (Explain your answer)
Fans doing the wave are making a transverse waves because the are
standing up and sitting down while the wave moves from one side of
them to the other. Therefore, the particles (people) are moving at right
angles to the direction of the wave.
Wave
Speed
v = λf
in (m/s)
Frequency
f = cycles/time
(Hz)
Period
Wavelength (λ)
in (m)
Amplitude (m)
A
v=3x2
v = 6 m/s
f = 4 cycles/2 sec
f = 2 Hz
X
3
2
B
v = 12 x 0.5
v = 6 m/s
f = 1 cycle/2 sec
f = 0.5 Hz
X
12
2
C
v=6x1
v = 6 m/s
f = 2 cycles/2 sec
f = 1 Hz
X
6
1
7. Draw two waves cycles “in phase (crest/crest and trough, trough
Give one wave an amplitude of 2 boxes and a wavelength of 4 boxes
Draw another wave with the same wavelength and an amplitude of 4 boxes
8. How many wave cycles are there between the arrows in the picture shown on
the right?
There are 3 wave cycles.
9. If the distant between the arrows is 180 cm, what is the wavelength of this
wave?
180 cm ÷3 wave cycles = 60 cm for each cycle (wavelength)
10. A swimmer at the beach notices that three wave crests pass a certain point
every 10.0 seconds. She also notes that each wave crest is about 2.0 meters apart.
What is the frequency of the wave that the swimmer is observing?
𝑓=
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑤𝑎𝑣𝑒𝑠
𝑡𝑖𝑚𝑒
So 𝑓 =
3 𝑤𝑎𝑣𝑒𝑠
10.0 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
so 𝑓 = 0.3 𝐻𝑧
What is the speed of the wave? The wavelength = 2.0 m
𝑣 = 𝜆𝑓 So 𝑣 = 2.0𝑚 × 0.3 𝐻𝑧
so 𝑣 = 0.6m/s
11. The wavelength of a sound wave in this room is 1.13 m and the frequency is
301 Hz. (remember, speed = wavelength x frequency or 𝑣 = 𝜆𝑓)
a.
What is the speed of the wave in the room?
𝑣 = 𝜆𝑓
so 𝑣 = 1.13𝑚 × 301𝐻𝑧
So 𝑣 = 340 𝑚/𝑠
b.
If you double the frequency of the sound wave, determine its speed.
So now 𝑣 = 1.13𝑚 × 602𝐻𝑧
𝑣 = 680 𝑚/𝑠
c. What happens to the wavelength if you cut the frequency in half? How do
you know?
Ignore this for now, we’ll discuss this in class.
12. A sound wave in a steel rail has a frequency of 620 Hz and a wavelength of
10.5 m. What is the speed of sound in steel?
𝒗 = 𝝀𝒇
so 𝒗 = 𝟏𝟎. 𝟓𝒎 × 𝟔𝟐𝟎𝑯𝒛
So 𝒗 = 𝟔𝟓𝟏𝟎 𝒎/𝒔
13. Explain how radio waves are made.
Radio waves are made when a current in a wire moves backwards and
forwards (oscillates). This creates a magnetic field which is also oscillating. This
oscillating magnetic field sends out electromagnetic waves.
14. Explain how the types of electromagnetic waves are arranged on the
electromagnetic spectrum.
The electromagnetic spectrum is arranged from radio waves, which are long
wavelength, low frequency, low energy waves to short wavelength, high
frequency, high energy gamma rays. As you move along the spectrum from
radio to gamma waves, the wavelength gets shorter and shorter while the
frequency and energy gets larger and larger.
15. What are several uses for electromagnetic waves?
•
•
•
•
•
•
•
•
Communication (radio waves, TV signals)
Determining location and speed of objects (RADAR which uses microwaves)
Cooking food (microwaves)
Detecting heat sources (infrared radiation)
Collecting visual information about our environment (visible light)
Sterilizing medical equipment and food (ultraviolet light)
Looking for injuries to bones (x-rays)
Treating cancer (gamma rays)
16. In what ways can electromagnetic waves be dangerous or harmful to living things?
• Sunburn, skin cancer, eye damage, aging of skin (UV)
• Deeper tissue damage and cancer (x-rays, gamma rays)
15.
A.
B.
C.
D.
E.
F.
Two waves combine to make a smaller wave. (SORRY FOR THE NUMBERING ERROR)
Constructive Interference
Absorption
Refraction
Reflection
Diffraction
Destructive Interference
17.
A.
B.
C.
D.
E.
F.
When a wave bends from one medium to another (like from air to water).
Absorption
Destructive Interference
Reflection
Diffraction
Constructive Interference
Refraction
18. Light comes back from a mirror by:
A. Diffraction
B. Absorption
C. Constructive Interference
D. Destructive Interference
E. Reflection
F. Refraction
20. When a wave goes from air to glass.
A. Diffraction
B. Absorption
C. Refraction
D. Destructive Interference
E. Reflection
F. Constructive Interference
19. Two waves that are completely inphase will make this:
A. Diffraction
B. Reflection
C. Absorption
D. Constructive Interference
E. Refraction
F. Destructive Interference
21. When a wave goes around a corner.
A. Constructive Interference
B. Destructive Interference
C. Absorption
D. Diffraction
E. Reflection
F. Refraction
22. X-rays
23. Wavelength
24. Frequency
25. Longitudinal
26. Reflection
27. Medium
28. Visible light
29. Mechanical
30. The crest
31. Diffraction
32. The trough
33. Interference
34. Amplitude
35. Electromagnetic
36. Transverse
37. Infrared
38. Doppler Effect
39. Ultraviolet
40. Refraction
41. Radio
42. Gamma