This document discusses waves and how they can be produced and observed using a ripple tank. It defines key terms used to describe waves, such as circular and plane water waves, and wavefront. It explains how waves are produced in a ripple tank using a dipper to disturb the water, and how their amplitude and frequency can be controlled. It describes how waves refract when passing between deep and shallow water, changing their speed and wavelength. It also explains how waves reflect off barriers, reflecting at equal angles to the normal.

1. WAVES AND ONLINE MEDIA…

2. August 15, 2014
Displacement-time (s-t) graph of Point P
s-d graph s-t graph
(a)
(b)
(d)
(c) (e)

3. 12.3 What are the terms used to describe waves?
Circular water waves
• Water waves are easily produced and
observed. By touching one point on
the surface, you can see the peaks of
the waves form circles and move
outwards from the source of
disturbance
• The line that joins all the peaks of a
wave or all identical points on a wave
is called the wavefront
• In the example at the right, the
wavefront is circular. The direction of
travel of circular waves is
perpendicular to the wavefront

4. 12.3 What are the terms used to describe waves?
Plane water waves
• Plane waves can be produced by disturbing the water surface
with a vibrating wooden bar
• The wavefronts of plane wave are straight lines
• The plane waves also travels in a direction perpendicular to
the wavefront

5. WAVE PRODUCTION AND THE RIPPLE TANK
 The bright and dark lines correspond to the crests
and troughs of the plane waves respectively.
 The depth at which the dipper is placed affects the
amplitude of the waves.
 The frequency of the waves is determined by the
frequency of vibration of the dipper.
A lamp is shone at a
shallow glass-bottomed
tray of a ripple tank.
Dark and bright lines
are formed on a screen
by the plane waves.

6. WAVE PRODUCTION AND THE RIPPLE TANK
Refraction of waves and depth of ripple tank
 The wavelength of the plane waves shorten as they travel
from deep to shallow water, i.e. λ2<λ1.
 The frequency remains unchanged as it is determined by
the dipper.
 Using v = ƒλ, the speed of waves is slower at the shallow
water, i.e. v2<v1
A plastic sheet creates a
shallow region of water. Speed and wavelength of waves
decrease from deep to shallow water.

7. WAVE PRODUCTION AND THE RIPPLE TANK
 Similar to light, when waves enter a region of
shallow water at an angle, the waves will refract.
If you place a plastic sheet at an angle, the change in
speed of the waves will cause them to bend.

8. WAVE PRODUCTION AND THE RIPPLE TANK
Reflection of waves
 A straight barrier standing upright in the water causes the
incoming waves to be reflected.
A straight barrier is placed at an angle to the straight
dipper. You can see the waves reflecting at equal
angles to the normal in the inset.

9. HTTP://EN.WIKIPEDIA.ORG/WIKI/WAVE_SHOALI

10. HTTP://EN.WIKIPEDIA.ORG/WIKI/WAVE_SHOALI