Review: What’s the difference between a transverse and longitudinal wave? What do waves transfer?...
-
Upload
kory-eaton -
Category
Documents
-
view
244 -
download
0
Transcript of Review: What’s the difference between a transverse and longitudinal wave? What do waves transfer?...
Review:What’s the difference between a transverse
and longitudinal wave?
What do waves transfer?
What are the high and low points of a transverse wave called?
What are the parts of a longitudinal wave where the particles are spread out and close
together?
First thing’s first…• Which of these show ONE full wave?
One wave has one crest and one trough
Wavelength• What is length a measure of?• So what do you think a wave length
is?– The distance between two wavesWAVELENGTH
WAVELENGTH
Which has a shorter wavelength?
Measuring Wavelength• Does this tell us the distance
between the two waves?• Why not?
You have to measure the distance between two comparable points!
(crest to crest, trough to trough, etc.)
Amplitude• The distance between the crest or
trough and the wave’s resting position.
• Where’s the crest? Trough?
Resting Position
Trough
Crest
Am
plitu
de
Am
plitu
de
Which has a larger amplitude?
What does amplitude tell us about a wave?
• Which of these waves would cause more damage if it hit the shore?
• Which has the larger amplitude?• Which wave has more energy?
THAT’S AMPLITUDE!
We’ve been looking at transverse waves…What about
longitudinal?• We can relate all of the parts of a
transverse wave to a longitudinal one!
We’ll start with wavelength…
• In a transverse wave:
• But there aren’t any crests or troughs in a longitudinal wave!
WAVELENGTH
WAVELENGTH
So we look at the compressions and rarefactions!• Compressions =
Crests• Rarefactions =
Troughs• Now we can find
the wavelength– Compression to
compression – Rarefaction to
rarefaction
On to amplitude…• In a transverse wave:
• We now know that compressions and rarefactions are like the crests and troughs, but it’s hard to find a longitudinal wave’s resting point.
Amplitude• For the amplitude
of a longitudinal wave, we look at how compressed or how rarefied the spring or particles are.– The more
compressed or rarefied it is, the higher the amplitude and vice versa.
Frequency• If your friend comes over to your
house “frequently”, how often do they come over?
• Can you take a guess as to what the “frequency” of a wave is?– The frequency of a wave tells us the
number of waves that are produced in a certain amount of time.
We need to know how many waves are being produced in
10 seconds.• How can you find the frequency of
this wave?• Step 1: pick a point.• Step 2: count the waves that pass
that point in 10 seconds.
Which has a higher frequency?
What about Energy?
Which wave did you have to put more energy into to create?
Waves with _________________frequency have
more energy.
What is the unit for frequency?
• Frequency is measured in Hertz (Hz).• If one full wave passes a point every
second, it has a frequency of 1 Hz.– 1 wave per second (1 wave/1 sec.)
• What is the frequency if three waves pass a point every second? – 3 Hz. (3 waves/1 second)
• What is the frequency if six waves pass a point every three seconds?– 2 Hz. (6 waves/3 seconds)
Wave Speed• There are two ways to calculate
wave speed.– Option 1: time how long a wave takes to
get from point A to point B.
A B
• Option 2: Use the following formula
Wave speed = wavelength x frequency
Wavelength – 2 meters
Frequency – 4 Hz.
(4 waves pass every second)
Wave Speed = 8 meters/second
• Wave speed is affected by several factors– The type of wave
• Example: electromagnetic waves always travel at the same speed in a vacuum (300,000 km/s – the speed of light)
– The medium the wave is moving through• If you start two waves in a pan, one with
water and one with corn syrup, which will reach the other side of the pan first?
• Another example is popping your knuckles underwater as opposed to above water.
Reflection
• Law of Reflection– The angle of incidence
equals the angle of reflection
Image position
• You think in straight lines!
• The image is located behind the mirror.
Refraction
• Sudden change in direction of a wave as it changes speed.– It must enter obliquely to change direction!
• Which direction does it bend as it slows?
Refraction
• In both cases the speed of the wave has decreased. This is indicated by the decrease in wavelength!
Refraction
• In which medium does light travel faster? (glass rod appears bent)
Refraction
• In simple terms, refraction is caused when a wave moves from one type of medium to another that has a different density. This makes objects between them look different.