J. Pulickeel SPH3U1 January 2010 Slide 2 2 Wave Behavior What
type of waves do not travel through a medium? What types of waves
travel through a medium? Name 3 types of these waves We know that
waves travel through mediums. But what happens when that medium
runs out? Slide 3 3 Boundary Behavior The behavior of a wave when
it reaches the end of its medium is called the waves BOUNDARY
BEHAVIOR. When one medium ends and another begins, that is called a
boundary. Slide 4 4 Fixed End One type of boundary that a wave may
encounter is that it may be attached to a fixed end. In this case,
the end of the medium will not be able to move. What is going to
happen if a wave pulse goes down this string and encounters the
fixed end? Slide 5 5 Fixed End Consider an incident pulse with an
upward pulse. What do you think will happen to the wave when it
hits the anchor? Click here for Phet Animation Slide 6 6 Fixed End
Animation The reflected pulse is upside-down. It is inverted. This
is because of Newtons Third Law. The wall is exert an equal in
magnitude but opposite in direction force back on the string, thus
causing the wave to return inverted. The reflected pulse has the
same speed, wavelength, and amplitude as the incident pulse. Slide
7 7 Free End Another boundary type is when a waves medium is
attached to a stationary object as a free end. In this situation,
the end of the medium is allowed to slide up and down. What would
happen in this case? If the end of an elastic rope is not fastened
to the pole then it will be free to move up and down. Slide 8 8
Free End Here the reflected pulse is not inverted. It is identical
to the incident pulse, except it is moving in the opposite
direction. The speed, wavelength, and amplitude are the same as the
incident pulse. Slide 9 9 Change in Medium Consider a boundary
condition where the medium of a wave changes. Think of a thin rope
attached to a thick rope. The point where the two ropes are
attached is the boundary. At this point, a wave pulse will transfer
from one medium to another. What will happen here? Slide 10 10
Change in Medium In this situation part of the wave is reflected,
and part of the wave is transmitted. Part of the wave energy is
transferred to the more dense medium, and part is reflected. The
transmitted pulse is upright, while the reflected pulse is
inverted. The denser material is somewhat like a fixed end because
it will offer resistance to the wave motion. But it is like a free
end also because it can move. Slide 11 11 Change in Medium The
speed and wavelength of the reflected wave remain the same, but the
amplitude decreases. The speed, wavelength, and amplitude of the
transmitted pulse are all smaller than in the incident pulse. The
frequency remains the same! Slide 12 12 Change in Medium Animation
Slide 13 13 Change in Medium Animation Slide 14 Sound Travelling in
the Same Medium What will travel faster: A high frequency or a low
frequency wave that is traveling in air? Do you hear high frequency
sounds faster than low frequency sounds? If you did, what would
this mean about music? Sound travels at the same speed in the same
medium. A high frequency would have a low wavelength! v =f Slide 15
6.5: Waves in 2D We have only been considering waves in 1 dimension
(eg. In a spring or rope). Consider how waves move in 2 Dimensions
Parallel rays through a convex lense will bend towards the normal.
Parallel rays through a concave lense will bend away from the
normal Slide 16 Slide 17 Waves and Wave Fronts Consider a wave
travelling in the ocean. The wave ray (or incident wave) indicates
the direction of transmission. The wavefront is the leading edge of
the wave. It is always to the wave ray Slide 18 Reflections of
Waves How would a light ray reflect off a plane boundary?
Reflecting surface Incident ray normal Angle of Incident i Angle of
Reflection r Reflected ray Slide 19 Reflections of Waves How would
a light ray reflect off a plane boundary? Reflecting surface
Incident wave normal Angle of Incident i Angle of Reflection r
Reflected wave Wavefront Slide 20 Waves at a Parabolic Surface
Slide 21 Refraction and Diffraction If a wave crosses the boundary
at an angle, the direction of travel changes. This is called
refraction. Incident wave Refracted wave Slide 22 Refraction and
Diffraction if the wave passes by the sharp edge of an obstacle or
through a small opening in the obstacle, the waves change
direction. This bending is called diffraction. Long-wavelength
waves are diffracted more than short-wavelength waves. Decreasing
the size of the opening will increase the amount of diffraction
Slide 23 Recall What will happen to a wave when it travels into a
denser medium? What is the difference between refraction and
diffraction? Draw the resulting wave front...
