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### Transcript of Waves - Weebly

PowerPoint Presentation– often through a disturbance in the
medium
pendulum
• Ex 1: find the period of a wave with a
frequency of 0.25 Hz
a period of 5 ms
s sHzf
with a frequency of 0.25 Hz
• Ex 2: find the angular velocity of an object
with a period of 5 ms
ω=2πf =2π(0.25Hz)
ω=2π/T =2π/0.005s
• Partner Purpose: to measure g
Procedure: refer to text, p. 5 but with the following changes: …
Observations:
0.10
0.15
0.20
0.25
0.30
0.35
• Since g
2 44
• Find g from your graph, then write a conclusion comparing your result to gravitational field g=9.8 m/s2
Simple Harmonic Motion
• Ex 3: sketch the graph of motion of the object from
example 1 if it started from 7cm above equilibrium position
x=7cos(1.5t)
v= -ωxosin(ωt)
v=-11sin(1.57t)
This gives:
v= 1.57 sqrt(7^2-2.7^2)
v=10.1cm s1
Start p. 107 #7-9
Bees can see in UV
• The mantis shrimp is a delightfully weird beastie. They’re multi-coloured, their genus and species names mean ‘mouth-feet’ and ‘genital-fingers’; they can move each eye independently, they see the world in 11 or 12 primary colours as opposed to our humble three, and now we find that this species can see a world invisible to the rest of us, said Professor White, of the University of Queensland.
• Mantis shrimps, dubbed “thumb splitters” by divers because of their vicious claws, have the most complex eyes in the animal kingdom, capable of seeing colors from the ultraviolet to the infrared, as well as detecting other subtle variations in light.
• They view the world in up to 12 primary colors- four times as many as humans - and can measure six different kinds of light polarization, Swiss and Australian researchers reported.
How damp is it?
How damp is it?
to friction, fluid resistance, etc.
The amount of damping can be classified as:
Start p. 107 #7-9
1. Waves were faster in the smaller slinky
2. Same
5. Only the disturbance travels
6. The waves reflected inverted (crest
reflected as a trough)
wavelength , we have:
v=f Ex 1: find the speed of a water wave with
wavelength 2.5 m and frequency 3 Hz
Don’t forget:
the bigger the better, and a microwave oven
to measure the speed of light
• Bring the chocolate for a Wednesday lab
day.
medium, we always find:
• The reflected wave will be:
– upright if the 2nd medium is less dense
– inverted if the 2nd medium is more dense
We can “see” wavelength as color

measured to be 14 cm
fc )102450(14.0 6
Ex 2: find the frequency of a 6.0 fm gamma
ray photon
– f=97.5 MHz
Total energy is a constant, depending on amplitude x
By conservation of energy, this also means:
Kinetic energy
Ex: find the kinetic energy for a 10 g mass on a spring
stretched 13 cm, when it is at a position of -3.5 cm
Potential energy can be found from other information,
e.g. Gravity or solved from total energy
Ex: find the potential energy for a spring stretched 13 cm,
when it is at a position of -3.5 cm
• Lab 8-4 p.160 Tuesday?
#1-2 p. 162 (reflection from parabola)
#1-3 p. 163 (diffraction)
• We find the waves are reflected with the same angle
Diffraction
• We get more diffraction with long wavelength, small opening
Refraction
• We can bend waves when they encounter a different medium
Start p. 125 #10-12
it resonates
and absorb those frequencies
found they pass through
space, they interfere
individual waves at each point
Wave Interference
the integer sum of the magnitudes.
• Draw the resultant of these two waves
interfering. Remember that the resultant
at each point is the integer sum of the
magnitudes.
Doppler effect with emitted light
• Blue shift: moving towards us
• Red shift: moving away
expanding!
• If the source is moving:
• Ex: find the frequency we hear for a 3000Hz sound from a car moving towards us at 25 m/s

• If the observer is moving:
• Ex: find the frequency we hear for a 250Hz sound if we run away at 13 m/s
Ex: find the frequency we hear for a 250Hz sound if we run away at 13
m/s
13330 250f
Hzf 240
Doppler formula
• For light:
• Ex: find the change in frequency we see for red light if a star moves away at 513,000 m/s
cf
f
Snell labs due Monday
• As the source moves faster through the medium, you can
see that the wavefronts start piling up in front of the
object, e.g. the “sound barrier.”
• Approaching the speed of sound the craft encounters the
sound waves piled on top of each other.
• Once the craft breaches the “sound barrier,” it leaves its
sound waves behind.
• The edges of these waves form a shock wave known as
the “sonic boom”
Labs due now
instantaneous