Download Longitudinal and Transverse Waves

Longitudinal
and Transverse
Waves
Learning Intentions
!
To develop an understanding of the properties of transverse and longitudinal
waves.
!
Success Criteria
!
You will be successful if you are able to...
!
Draw a transverse wave and label; crest trough, wavelength, null position
and amplitude.
!
Give the symbols for wavelength and amplitude.
!
Draw a diagram showing the direction of wave motion and direction of
material motion in longitudinal and transverse waves.
!
Define wave speed as the distance travelled by the wave per second.
!
Solve problems with waves using the equation v=d/t
Wavelength
Crest
λ
Amplitude (A)
λ
Null Position
λ
Trough
Wavelength is the distance between similar points on the wave
Transverse Waves
Learning Intentions
!
To develop an understanding of the properties of transverse and longitudinal
waves.
!
Success Criteria
!
You will be successful if you are able to...
!
Draw a transverse wave and label; crest trough, wavelength, null position
and amplitude.
!
Give the symbols for wavelength and amplitude.
!
Draw a diagram showing the direction of wave motion and direction of
material motion in longitudinal and transverse waves.
!
Define wave speed as the distance travelled by the wave per second.
!
Solve problems with waves using the equation v=d/t
Transverse
Waves
In a transverse wave
Motion of the material
the substance moves
perpendicular to the
direction of motion
Direction
of the wave.
of Travel
Transverse Wave
Animation
Animation courtesy of Dr. Dan Russell, Grad. Prog. Acoustics, Penn State
Longitudinal Waves
Direction of Travel
Motion of the
material
In a longitudinal
wave the substance
moves parallel to
the direction of
motion of the wave.
Longitudinal Wave
Animation
Animation courtesy of Dr. Dan Russell, Grad. Prog. Acoustics, Penn State
Learning Intentions
!
To develop an understanding of the properties of transverse and longitudinal
waves.
!
Success Criteria
!
You will be successful if you are able to...
!
Draw a transverse wave and label; crest trough, wavelength, null position
and amplitude.
!
Give the symbols for wavelength and amplitude.
!
Draw a diagram showing the direction of wave motion and direction of
material motion in longitudinal and transverse waves.
!
Define wave speed as the distance travelled by the wave per second.
!
Solve problems with waves using the equation v=d/t
Reminder - Distance, Speed and Time Formula
Wave speed
meters per second
m/s or ms-1
Time
(seconds - s )
Distance
travelled by
the wave
(meters - m)
Lesson 2
Frequency
National 4
National 4
v
1 Hertz Wave
Fixed point
Frequency
0 waves
Counter
0s0
Timer
National 4
v
1 Hertz Wave
Frequency
1 wave
Counter
1s0
Timer
National 4
v
1 Hertz Wave
Fixed point
Frequency
2 waves
Counter
2s0
Timer
Lesson 3
Frequency from
a
Graph
!
and consolidation
National 4
Finding Frequency from a Graph
Amplitude (m)
0 1 2 3 4 5 6 7 8
time (s)
National 4
Diffraction
National 4
Learning Intentions
!
To develop an understanding diffraction of waves.
!
Success Criteria
!
Will have observed and sketched diagrams of the diffraction of waves in
some simple situations.
!
Will be able to give a definition of diffraction
!
Will be able to describe examples of diffraction occurring with radio
waves.
!
State the relationship between wavelength and size of the diffraction
which occurs.
Diffraction through a gap
Short Wavelength
Diffraction through a gap
Long Wavelength
•The wavelength, frequency and speed are same
before and after diffraction. The only change is the
direction in which the wave is travelling.
!
•The diffraction effect is greatest when the width of
the gap is about the same size as the wavelength
of the wave.
Diffraction of Radio Waves
Short Wave Diffraction
Diffraction around an obstacle
Short Wavelength
TV and FM Radio Signals have a
wavelength of around few metres
(microwaves) which allow for higher
data transmission. However this
means they cannot diffract over or
around hills.
Long Wave Diffraction
Diffraction around an obstacle
Long wavelength
Long-wave radio is transmitted using
waves with a wavelength of around
1km. This means they can diffract
around objects including hills and
buildings; they can reach places that
short-wave radio cannot. This is why it
is often possible to listen to long wave
radio stations such as radio 4, even
when FM reception is poor.
Telescopes
cameras
National 5
Refraction
Binoculars
Microscopes
Learning Intentions
To explore the refraction of light.
Success Criteria
You will be successful if you can...
!Explored what happens to a ray of light as it passes
into and out of a glass block at different angles.
! Use correctly the terms
• Angle of incidence.
• Angle of refraction.
• Normal
! Explain refraction in terms of change of wave speed.
Ray Diagram
How do you draw a ray diagram?
Ray Diagram
You will need:
Power Supply (12V)
Ray box
Rectangular Prism
Paper
Sharp Pencil
Ruler
Put your bag under
your desk!
Refraction in Action
Can you
explain how
objects appear
to separate
underwater?
Ray Diagram
Angle of
incidence
Angle of
refraction
Normal
Normal
Angle of
incidence
Angle of
refraction
Refraction is the change in the direction of light when it moves
from one material to another due to the light changing speed.
Remember FAST
Faster
Away
Slower
Towards
When light travels into a LESS
dense material it’s speed increases
and the light rays bend AWAY
from the normal
When light travels into a MORE
dense material it’s speed
decreases and the light rays bend
TOWARDS the normal
Appear to Disappear
Willebrord Snellius studied the laws of
refraction in the 17th Century.
!
A materials refractive index describes
how light travels through the material.
!
Light will travel through materials at
the same speed if they have the same
refractive index
??Question time??
The ray diagram shows light moving
from air into glass.Write an explanation
of why the ray moves in such a way.
Include these words: refraction, incident
ray, refracted ray, denser, towards or
away and medium.
Air
Glass
Learning Intentions
To explore the refraction of light.
Success Criteria
You will be successful if you can...
!Explored what happens to a ray of light as it passes
into and out of a glass block at different angles.
! Use correctly the terms
• Angle of incidence.
• Angle of refraction.
• Normal
! Explain refraction in terms of change of wave speed.
Refraction Explained
Refraction/change in speed link
Lesson 2
Critical angle and total
Internal reflection
Telescopes
cameras
Critical angle and
total
Internal reflection
Binoculars
Microscopes
Learning Intentions
To explore the refraction of light.
Success Criteria
•You will be successful if you can...
•State what happens to a refracted ray when moving
from glass to air.
•State that above the critical angle total internal
reflection occurs.
•Be able to give an example of the practical use of total
internal reflection.
Ray Diagram
Angle of
incidence
Angle of
refraction
Normal
Normal
Angle of
incidence
Angle of
refraction
Refraction is the change in the direction of light when it moves
from one material to another due to the light changing speed.
Total Internal Reflection
Describe what happens when this angle is increased.
Applications of Total Internal Reflection
Making Optical Fibres Video
Heartburn and Acid Reflux Testing - Endoscopy
Corning Optical Fibre video (Detailed but difficult)
Total Internal Reflection
Ultimate Physics Pg18