Properties of waves
1.
Waves in shallow water near a beach are travelling with a speed of 3.00 m s-1.
(a)
A surfer is waiting to catch a wave. If large waves on a particular day are on average
25.0 m apart, how long does the surfer have to wait between waves?
(2 marks)
(b)
On a different day and in choppy surf, the waves are arriving at the shore every 4.00 s.
What is the period and frequency of the wave?
(2 marks)
(c)
What is the distance between the crest of the waves in the choppy surf if they are still
travelling at 3.00 m s-1.
(2 marks)
2.
(d)
After finishing surfing, the surfer is standing on top of a cliff watching the waves below.
He observes that other surfers that are further out than where the waves begin to break are
bobbing on their boards but not moving closer to the shore. In the context of waves, why
are the surfers not moving with the wave towards the shore?
(a)
Bats emit very high pitched sound waves. The shortest wavelength emitted in air by a bat
is about 3.30 mm. What is the highest frequency sound that a bat is able to emit? (2 marks)
(b)
Would humans be able to hear these sounds? Explain your answer.
(2 marks)
SOLUTIONS
1.
a.
b. Period = 4.00 s.
c.
d. The waves (and all waves) only transfer energy and not matter. The waves would not
push the surfers towards the shore, only up and down as the wave disturbs the position
of the water.
2.
a.
b. No. The threshold of human hearing is around 20 kHz which is lower than the frequency
of the sound produced by the bat.