Chapter 1: Waves

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Chapter 1 Waves
Form 5
Physics
Next gt
The study of matter
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Objectives (what you will learn)
1) understanding Waves2) reflection of
waves3) refraction of waves4) diffraction of
waves5) interference of waves6) analysing
sound waves7) analysing electromagnetic waves
Physics Chapter 1
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Understanding Waves
Physics
1. A wave is a traveling disturbance from a
vibrating or oscillating source.
2. A wave carries energy along with it in the
direction of its propagation.
3. A wave is a mean of energy transfer through
vibration.
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Transverse Wave
Waves
Particles in the medium vibrate in a direction
perpendicular to the direction of wave
propagation.Perpendicular 90o to theline of
direction.Exampleswave in a ropewater
waveslight waves
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Longitudinal Wave
Waves
Particles in the medium vibrate in a direction
parallel (0o to line of direction) to the
direction of wave propagation.Exampleswave in
a slinky springsound wave
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Surface Waves
Waves
This is both transverse waves longitudinal
waves mixed in one medium.Examplesearthquake
or seismic waveshear wave in a slinky spring
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Waves
Complete Oscillation
Complete cycle e.g. motion from A to B back
to A.
Amplitude, a
Maximum displacement from equilibrium position
that is halfway between crest (high) trough
(low).
Period, T
Time taken for a complete oscillation.
Frequency, f
Number of complete oscillation in one second
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f 1/T
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Waves
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Waves
Damped Oscillation
An oscillation whose amplitude decreases due to
energy loss from the system (as heat to air
resistance).
Forced Oscillation
An oscillation produced when a system is forced
into oscillation by an external periodic force.
Resonance
Occurs when a system which is forced into
oscillation oscillates with large amplitude the
condition being that the frequencies of both
systems are equal to each other.
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Reflection of Waves
Angle of reflection angle of incidence
Reflected wave has same speed, frequency,
wavelength as the incident wave.
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Angle of reflection, r Angle of incidence, i
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Refraction of Waves
Refraction of wave
The change in velocity of wave when it travels
from one medium to another.Water light waves
are refracted towards Normal when moving into
shallower or denser region (frequency unchanged,
speed wavelength decrease), and away from
Normal the other way round. But sound waves
behave in the opposite way.(Try relate it to
theresistances of medium)
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Diffraction of Waves
Diffraction is the spreading of waves after
passing a narrow slit or an obstacle.Waves are
diffracted more if
a. the slit is narrower
b. the wavelength is longer
Light has very short wavelengths, diffraction
occurs only for slits with width of 10-4 m or
less.
Sound has long wavelengths, diffraction of sound
waves enable sound to go around corners.
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Interference of Waves
Principle of superposition of waves
Displacement y, produced by 2 waves at a point is
the vector sum of displacements y1 y2 produced
by each of the waves.
y y1 y2
Interference effect produced by superposition
of waves from 2 coherent sources. Coherent
sources if they oscillate in phase, or
antiphase, or with same phase difference they
have the same frequency.
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Interference of Waves
antinode constructive superposition from 2
crests or troughsnode destructive
superposition from crest trough
Separation between 2 consecutive antinodal or
nodal lines at distance D from the 2 sources
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Youngs double-slit experiment
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Sound Waves
Sound waves are produced by vibrating sources.
They are longitudinal waves requiring a medium
for propagation. It cannot travel in vacuum.
Applications of reflection of sound wave
a. sonar or high frequency sound waves used to
determine depth of ocean
b. Ultrasonography uses ultrasound waves to
examine condition of fetus, the reflected waves
used to form an image on a monitor.
c. Ultrasound is also used to detect tumour in
the body
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d. Reflection of ultrasound from rocks used in
geological survey.
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Electromagnetic Waves
Common properties
a. Need no medium, can travel in vacuum.
b. Travels at constant speed of light, c 3 x
108 m s-1 in vacuum.
c. Transverse waves.
d. Wave properties like reflection, refraction,
diffraction interference.
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Summary
What you have learned

• Understanding Waves

• Reflection of waves

lt Back
3. Refraction of waves
4. Diffraction of waves
5. Interference of waves
6. Sound electromagnetic waves
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Thank You