Question description
Lab
Assignment 11: Properties of WavesInstructor’s OverviewIf you think carefully about it, we are
immersed in waves. The fact that you can
turn on a radio and listen to music or news, or receive a cell phone call is
evidence of the transmission and reception of waves. These two examples involve transverse
electromagnetic waves. Having a
conversation with a family member, friend, or colleague is made possible by
longitudinal waves of sound. Waves
transmit energy and demonstrate interesting properties such as superposition
(constructive/destructive interference) and resonance. We’ll explore many of the properties of waves
in this final lab of Physics I.This activity is based on Labs 21 and 24
of the eScience Lab kit.Our lab consists of three main
components. These components are
described in detail in the eScience manual.
Here is a quick overview:
eScience Lab
21 Experiment 1: In the
first part of the lab, you will use a Slinky® to create and
visualize transverse and longitudinal waves. You’ll experiment with wave reflection,
superposition, and resonance.
eScience Lab
21 Experiment 2: In the
second part of the lab, you will create your own wave source using a cork
and a tub of water. This
experimental setup allows you to explore the Doppler effect.
eScience Lab
24 Experiment 2:In the final
part of the lab you will explore the concepts of pitch and resonance by
experimenting with water-filled bottles.
Take detailed
notes as you perform the experiment and fill out the sections below. This document serves as your lab report. Please include detailed descriptions of your
experimental methods and observations.Experiment Tips:
·
In
general, read the lab questions below before running the experiments. This allows you to keep an eye out for
specific things as you run the experiments.·
Make
sure to run the Slinky® experiments on a hard floor. Carpeted floors dampen the wave behavior and
make the experiments more ambiguous.·
For
the Doppler effect experiment, it is easier to see the wave behavior with a
larger tub of water. Wave reflection
from the sides of small tubs make the observations more challenging.·
Narrow
neck glass bottles work well for the sound experiments in eScience Lab 24.Date: Student: AbstractBackgroundObjectiveHypothesisIntroductionMaterial and MethodsResultseScience Lab 21 Experiment 1: Slinky®Based on your
results from the Slinky® experiments, please answer the following
questions:1. What happened when the transverse waves
reached your partner’s end? Did the reflected wave stay on the same side as the
one you sent? Draw a diagram showing the incoming and reflected waves.2. Did the waves go any faster or slower when
you tried a variety of amplitudes? Explain how this agrees or disagrees with
the equation for a transverse wave’s velocity.3. What did you notice about the speed of the
longitudinal waves compared to the transverse waves?4. Explain what happened when you and your
partner both sent waves on the same side. What kind of interference took place?5. What happened when waves on opposite sides
passed each other?6. How did shortening the length of the
spring affect the resonant frequencies? How does this confirm the relationship
v = λ f when velocity is constant? (Hint: a shorter spring length means smaller
wavelengths for each standing wave).7. Using this knowledge, explain how musical
instruments create higher and lower tones. Use a string instrument as an
example.eScience Lab 21 Experiment 2: Doppler EffectBased on your
results from the cork and water experiment, please answer the following
questions:1. Draw a picture of a moving source and the waves
surrounding it according to what you observed in this experiment. How does the
spacing of the wavefronts in front of the source compare to those behind it?2. Imagine a small observer is positioned in front of
cork in your picture above. As the cork approaches, the observer measures the
wavelength of the waves passing by. How does this wavelength compare to that
measured from behind the source?3. Imagine that this same observer measures the frequency
of the waves instead of wavelength. How does the frequency measured in front of
the source appear to the observer compared to the frequency measured from
behind?4. How do these results help explain why a car’s engine
sounds different as the car approaches you compared with after it passes?5. The Doppler effect is present in light waves as well.
As you will learn in Physics II, red
light has a lower frequency than blue light. Based on your observations in this
experiment, what can you speculate about the motion of a distant star that
appears “red‐shifted” to astrophysicists? (The light appears more
red than expected.)eScience Lab 24 Experiment 2: Pitch and ResonanceBased on your
results from water bottle experiments, please answer the following questions:1. Did the pitch of the noise made by
striking the bottle get higher or lower as you filled the bottle with water?2. Did the pitch made by blowing across the
top of the bottle go up or down as you filled the bottle?3. Why is there a difference between these
two noises? In your answer, comment on the source of the noise in each case (i.e.
What is vibrating?).4. Using what you know about harmonics and
resonance, explain how different pitches are created when you blow across the
bottle opening with different liquid levels.5. What wave property allowed you to hear
noise through your bottle in step 2 of Procedure 2, and how does the sound
transmit from one bottle to the other? Did the pitch sound the same as the one
made by your partner?ConclusionsReferences
