PowerPoint PresentationPhysics
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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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Waves
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Particles in the medium vibrate in a direction perpendicular to the direction of wave propagation.
Perpendicular
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Particles in the medium vibrate in a direction parallel (0o to line of direction) to the direction of wave propagation.
Examples:
sound wave
This is both transverse waves & longitudinal waves mixed in one medium.
Examples:
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Wavefront
A surface on the wave where all particles vibrate in phase (coming together to the same level).
Oscillations
Vibration or oscillation of particles in a medium is like oscillation of simple pendulum or loaded spring.
http://web.ics.purdue.edu/~braile/edumod/slinky/slinky.htm
Amplitude, a
Maximum displacement from equilibrium position that is halfway between crest (high) & trough (low).
Period, T
Frequency, f
f = 1/T
Free Oscillation
Occurs when a system oscillates without any external force acting on it.
Natural Frequency, fn
Simple pendulum
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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Angle of reflection = angle of incidence
Reflected wave has same speed, frequency, & wavelength as the incident wave.
Angle of reflection, r = Angle of incidence, i
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λ
λ
i
r
v
v
Links:
http://en.wikipedia.org/wiki/Ruler
http://www.notesandsketches.co.uk/Measuring-marking-out.htm
http://en.wikipedia.org/wiki/Calipers
http://en.wikipedia.org/wiki/Micrometer
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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.
resistances of medium)
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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http://www.bbc.co.uk/scotland/education/bitesize/higher/physics/radiation/waves1_rev.shtml
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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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node:
destructive superposition from crest & trough
Separation between 2 consecutive antinodal or nodal lines at distance D from
the 2 sources:
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
d. Reflection of ultrasound from rocks used in geological survey.
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b. Travels at constant speed of light,
c = 3 x 108 m s-1 in vacuum.
c. Transverse waves.
Name
Sources
Applications
Visible light
Sun, lamps
X-rays
Gamma rays
Radioactive nuclei
Radiotherapy, sterilizer