Waves at Boundaries Worksheet
1. A pulse is sent along a spring. The spring is attached to a light thread that is tied
to the wall in the figure below.
a)
b)
c)
d)
What happens when the pulse reaches point A?
Is the pulse reflected from A erect or inverted?
What happens when the transmitted pulse reaches B?
Is the pulse reflected from B erect or inverted?
2. A long spring runs across the floor of a room and out the door. A pulse is sent along
the spring. After a few seconds, an inverted pulse returns. Is the spring attached to the
wall in the next room or it is lying loose on the floor?
3. If you want to increase the wavelength of waves in a rope, should you shake it at a
higher or lower frequency?
4. A pulse is sent along a thin rope that is attached to a thick rope. The thick rope is
itself tied to a wall, as shown below.
a)
b)
c)
d)
What happens when the pulse reaches point A?
Is the pulse reflected from A erect or inverted?
What happens when the transmitted pulse reaches B?
Is the pulse reflected from B erect or inverted?
Questions 5, 6, 8 on page 353.
Boundaries
1. What is the relationship between the amplitude of a wave and the energy carried
through the wave?
2. When a wave reaches the boundary of a new medium, part of the wave is
reflected and part transmitted. What determines the comparative sizes of the
reflective and transmitted wave?
3. A pulse reaches the boundary of a new medium more dense than the one from
which it came. Is the reflected pulse erect or inverted?
4. Waves are sent along a spring of fixed length.
a. Can the speed of the waves in the spring be changed? Explain.
b. Can the frequency of a wave in the spring be changed? Explain.
5. You repeatedly dip your finger into a sink full of water to make circular waves.
What happens to the wavelength, velocity, and frequency as you move your finger
faster?
Page 343, Questions 3, 4, 7
Interference of Waves
1. If a rain drop falls into a pool, small-amplitude waves result. If a swimmer jumps
into a pool, a wave of large amplitude results. Why doesn’t the heavy rain in a
thunderstorm produce large waves?
2. You can make water slosh back and forth in a shallow pan only if you shake the
pan with the correct frequency. Explain.
3. A large erect wave pulse is moving to the left on a large spring at the same time
that a smaller inverted wave is moving to the right. Describe what the spring will
look like as the waves pass through one another.
4. An apparatus is made by extending a string horizontally between two poles. Four
pendulums are constructed of a weight and a string and hung from the horizontal
string, as shown below. Two pendulums are the same length (A and C), one
pendulum is longer (B) and one pendulum is shorter (D). One at a time, each
pendulum is pulled to the side and released. Describe what happens to the other
pendulums in each case.