This ppt discusses the relationship of wavelength and frequency to the speed of the wave.

1. Do now!
Can you write the
title “WAVE
EQUATION” in
your NOTE
BOOK please?
(DO NOT
FORGET THE
LECTURE
NUMBER)

2. WAVE EQUATION

3. What is a wave?
YouTube - Water bubble in Space (zero gravity)
http://www.youtube.com/watch?v=xUnadiyPTks

4. Waves
Waves can transfer energy and
information without a net motion of the
medium through which they travel.
They involve vibrations (oscillations) of
some sort.
Can you do something very boring
and traditional………
Can you copy this please?

5. Rays highlight the direction
of energy transfer.
Light
RAY
UV
RAY
GAMMA
RAY

6. Transverse
waves
The oscillations are perpendicular to the direction
of energy transfer.
Direction of energy transfer
Oscillations CREST
Trough

7. Transverse waves
•Water ripples
•Light
•On a rope/slinky
•Earthquake

8. Longitudinal waves
The oscillations are parallel to the direction
of energy transfer.
Direction of energy transfer
oscillation

9. Longitudinal waves
compression
rarefaction

10. Longitudinal waves
•Sound
•Slinky
•Earthquake

11. Wave measurements

12. Amplitude - A
The maximum displacement from the mean
position.
Amplitude
THE MAXIMUM DISPLACEMENT FROM
THE NORMAL LINE OR EQUILIBRIUM
Equilibrium/
normal line

13. The time taken (in seconds) for
one complete oscillation. It is also
the time taken for a complete
wave to pass a given point is
called PERIOD.
One complete wave

14. Frequency - f
The number of oscillations in
one second. Measured in Hertz.
50 Hz = 50
vibrations/waves/oscillations in
one second.

15. Period and frequency
Period and frequency are
reciprocals of each other
f = 1/T T = 1/f

16. Wavelength - λ
The length of one complete wave.
wavelength
THE LENGTH OF ONE COMPLETE
WAVE

17. Wave speed - v
The speed at which the wave fronts pass a
stationary observer.
YouTube - Bill Nye the Science Guy - 51: Waves 1/3
THE SPEED AT WHICH THE WAVE
FRONTS PASS A STATIONARY
OBSERVER

18. The Wave Equation
v = fλ
v = speed (m/s)
λ = wavelength (m)
f = frequency (Hz)
v
λf x

19. 1)A water wave has a frequency of 2Hz and
a wavelength of 0.3m. How fast is it
moving?
2)A water wave travels through a pond with
a speed of 1m/s and a frequency of 5Hz.
What is the wavelength of the waves?
Some example wave equation questions
0.2m
0.6m/s

20. 3.)The speed of sound is 330m/s (in air).
When Dave hears this sound his ear
vibrates 660 times a second. What was
the wavelength of the sound?
4.)Purple light has a wavelength of
around 6x10-7m and a frequency of
5x1014Hz. What is the speed of purple
light?
0.5m
3x108m/s

21. SAMPLE PROBLEM
•1. A wave has frequency of 50 Hz
and a wavelength of 10 m. What is
the speed of the wave?
•2. A wave has frequency of 5 Hz
and a speed of 25 m/s. What is the
wavelength of the wave?
500m/s
5m

22. •3) A wave has wavelength of 10 m and a
speed of 340 m/s. What is the frequency of
the wave?
•4. The speed of a wave is 65 m/sec. If the
wavelength of the wave is 0.8 meters, what
is the frequency of the wave?
•5. A wave with a frequency of 500 Hz is
traveling at a speed of 200 m/s. What is the
wavelength?
34 Hertz/ 34 vib/sec
85 Hertz/ 85
vib/sec
0.4m

23. Wave equation questions
v
λf x

24. •1. As the wavelength of a
wave in a uniform medium
increases, its speed will _____.
a. decrease
b. increase
c. remain the same

25. EXPLANATION
•ALL EM WAVES TRAVEL AT THE SPEED
OF LIGHT REGARDLESS OF THE
FREQUENCY AND WAVELENGHT.
•The speed of light is close to 300,000 km/s
(186,300 miles per second).
•Another way of writing this is: 3x 108m/s -1

26. 2. As the wavelength of a wave
in a uniform medium increases,
its frequency will _____.
a. decrease
b. increase
c. remain the same

27. Let’s try some questions!
ACTIVITY
TIME!

28. ACTIVITY NO____
SPEED (m/s) Wavelength (m) Frequency (Hz)
1._______ 9m 4Hz
36m/s 2.________ 6Hz
330m/s 27m 3. ________
750m/s 4. _______ 10Hz
5.________ 250m 15 Hz
6.________ 2m 3Hz

29. LET’S CHECK!

30. ACTIVITY NO____
SPEED (m/s) Wavelength (m) Frequency (Hz)
1._______ 9m 4Hz
36m/s 2.________ 6Hz
330m/s 27m 3. ________
750m/s 4. _______ 10Hz
5.________ 250m 15 Hz
6.________ 2m 3Hz
36m/s
6m
12.2 Hz
75m
3750m/s
6m/s