introduction into waves

1. • How could you hear my voice now?
• Very well, with your ears
• That is right, but
• What make my voice reach your ears to hear it ?
• And how did that happen ?
• ……………………………………………………………
• Also think about,
• Why could the light comes from The Sun to The Earth and
How ?
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2. Introduction into
Waves

3. DO YOU THINK ABOUT THESE WAVES?
But,
That is an example for only one type of waves.
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4. FIRST,
WHAT ARE WAVES ?
• A Wave :
– A disturbance that carries energy from
one place to another.
• Waves only transfer energy.
• Waves do not transfer matter. How?
• Waves need a medium to transfer.
• A Medium :
• The material through which the waves travels.
BUT:
Some waves do not need a medium to
be able to move.
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5. lets discover the types of waves..
According to the way to
transfer
According
to the
medium
Electromagnetic Wave
A wave can travel without a
medium, (through space)
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6. 1. TRANSVERSE WAVES
• Waves in which the medium moves
at perpendicularly to the direction
of the wave.
• Parts of transverse waves:
– Crest: the highest point of the wave
– Trough: the lowest point of the wave
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7. 2. Compressional (longitudinal) waves:
• Waves in which the medium moves back and
forth in the same direction as the wave.
• Parts of compressional waves:
– Compression: where the particles are close
together
– Rarefaction: where the particles are spread
apart
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8. 3. Mechanical Wave :
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9. 4. Electromagnetic Wave:
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11. Lesson 2
Properties of waves

12. • Wave properties
• Descriptive wave properties include:
1. Wavelength (λ):
-
- Or, The distance between two consecutive crests or troughs of a transverse wave.
- Or, The distance between two consecutive compressions or rarefactions of a wave.
>------- Wavelength---<
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13. 2. Frequency (f):
The unit of measurement is
• The higher the frequency, the more energy in
the wave.
– If 10 waves go past in 1 second, it is 10 Hz
– If 1,000 waves go past in 1 second, it is
– If 1,000,000 waves go past, it is 1,000,000 Hz
3. The Wave Period (T):
 So, the period is the reciprocal of the
frequency.
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14. 4. Amplitude (A):
– How far the medium (crests and troughs,
or compressions and rarefactions) moves
from rest position (the place the medium
when not moving).
• The more energy a wave carries, the larger
its amplitude.
5. Wave speed (v):
Depends on the medium in which the
wave is traveling.
• It varies in solids, liquids and gases.
• A mathematical way to calculate wave
speed is:
1. wave speed = wavelength (m) x frequency
(Hz). Or, v = f x λ.
2. wave speed = wavelength (m) / wave period
(s). Or, v = λ / T.
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15. • if a wave has a wavelength of 5 m and a frequency of 30
what is its speed?
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16. •a = …………………….......……………..
•b = ……………………………………....
•c = …………………………....…………..
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17. •The speed of any wave depends upon
A. its energy.
B. the medium through which it travels.
C. its angle of reflection.
D. its amplitude.
• Which of the following statements illustrates the concept that
waves carry energy from one place to another:
A. Ocean waves may cause boats to tip over.
B. Sunlight heats the surface of the earth.
C. Seismic waves cause earthquake damage.
D. All of the statements illustrate the concept.
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