Transcript Waves - science

21 July, 2015
Sound
Objectives
Be able to describe what a sound is and how its pitch
can be altered.
HSW: AF4 – Using investigative approaches
Used before in:
Will use again in:
PLTS: Team Workers: collaborate with others to work towards a common goal.
Used before in:
Will use again in:
Keywords
Infrared, visible, EM Spectrum, remote control, digital,
photography.
1 of 43
OUTCOMES
• ALL MUST be able to describe what a sound
is.
• The pitch of a note increases as the
frequency increases.
• The loudness of a note increases as the
amplitude of the wave increases.
• MOST SHOULD know how to compare the
amplitudes and frequencies of sounds from
diagrams of oscilloscope traces.
• SOME COULD be able to explain how the
design of musical instruments affects their
sound and pitch.
2 of 43
3 of 43
SOUND Starter
KEYWORD SCRAMBLE: UNSCRAMBLE THE WORD AND WRITE A DEFINITION. THE FIRST PERSON
TO DO THE MOST IN 6 MINS WINS)
WORD
vbiaritons
ncyquefre
ztreh
waltenvegh
plitudeam
deeps
osiclolcospe
tongillunida
pierod
4 of 43
Definition
Word
Definition
Vibrations
A movement of a particle about a fixed point
Frequency
The amount of vibrations in a second
Hertz
The unit of frequency (same as 1/s)
Wavelength
The distance between to consecutive similar points on a
wave (ie peak to peak)
Amplitude
The distance from the centre to the peak or trough of the
wave. (the loudness)
Speed
The distance an object travels in a given time
Oscilloscope
A device that can show electrical signals on a screen
Longitudinal
A wave where the particles travel parallel to the direction of
the wave.
Period
The time for one wave in seconds (1/frequency)
5 of 43
Introduction
• http://www.ltscotland.org.uk/5to14/resources/science/speedofsound.
asp Show the speed of sound animation. What would happen if I hit
it harder? Would it go quicker? Show:
http://www.ltscotland.org.uk/5to14/resources/science/sound/soundp
ulse.asp to explain.
• What is a sound wave?
• Demo how to make some different sounds.
• Demo a speaker cones vibration with rice on it.
• Connect it to a signal generator in order to get different pitches and
see what is happening. Demo slinky.
• Look at sound waves in solids and gases:
http://www.ltscotland.org.uk/5to14/resources/science/sound/index.as
p and then
6 of 43
Studying waveforms in the classroom
An oscilloscope is an
instrument that detects a
varying voltage from an
input, such as a
microphone, and plots its
waveform against time.
A signal generator
produces an alternating
voltage at a chosen
frequency and amplitude.
It can also produce a range
of different waveforms.
7 of 43
Using an oscilloscope
8 of 43
• Demos
9 of 43
Understanding waves and waveforms
10 of 43
Straw Oboe
Flatten one end of the soda straw by sticking the end in your mouth, biting down with your teeth and pulling it
out. Do this several times to make a nice flexible flat ended straw.
Cut a piece of straw from each side of the flat region making the straw have two lips at the end.
Cut two edges off the flattened end of a straw.
Put the straw in your mouth, bite down on it gently with your front teeth just beyond the cut end.
Bite down with your teeth just beyond the cut end of the straw.
Experiment with blowing hard and soft while biting down hard and soft until you make the straw sing.
11 of 43
Plenary
• Vibrations cause sound as a ………….. wave.
• The speed of sound in air is ……m/s.
• Sound travels faster in ………. and faster again
in solids because the particles are ………..
together.
• Since it is a wave it can be reflected (echo) and
………….
• Sound cannot travel through a ……. (In space
nobody can hear you scream.)
• If the frequency is higher the ………. is too.
12 of 43