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A cura della 4 A L.S.
Docente: Lucia Russo
• A wave is an oscillation accompanied by a
transfer of energy , but not substance, that
travels through space or mass.
• An example of wave is the drop of water that falls
into a puddle - it produces a circular ripple.
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PHISICAL QUANTITIES LINKED TO
WAVES:
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• Wavelength: spatial period of the wave. It is theNono
distance
between
two crests orto
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two troughs. The crest is the point on a wave with theedit
maximum
The trough
is theFate
lowest
point
on ailwave.
is designated
by the Greek
letter
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• Frequency: number of occurrences of a repeating event in the period (=duration
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of time of one cycle in a repeating event).
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• Phase velocity: rate
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which
the phase of the wave propagates
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space. This is the velocity
at which
the phase of any component
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ofthe
wave
frequency
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KIND OF WAVES:
(BY PROPAGATION)
• Longitudinal waves: when
the oscillations are parallel
to the direction of energy
propagation.
• Traversal waves: when
the oscillation are
perpendicular to the
direction of energy
transfer.
KIND OF WAVES:
• Mechanical wave: a
wave that creates
oscillation of matter.
Its movement is
limited and it
transfers energy.
(SOUND)
• Elastic wave: a
wave that moves
through to an
elastic material.
(LIGHT )
Sound is a wave created by vibrating
objects and propagated through a medium
from one location to another.
EAR
The ear is the organ that detects sound.
It receives sound and influences
balance and body position. The ear is
part of the auditory system. The ear
has three main parts: the outer ear,
middle ear, and inner ear.
PROPERTIES OF THE SOUND
FREQUENCY
Name
Infrasonic
Sonic (AKA
Audio)
Ultrasonic
Frequency Range (Hz)
Characteristics
0 - 20
Very low frequencies of sound that the
human ear can’t detect, but you may
feel the rumbling of the waves through
your body.
20 - 20 000
Normal range for human ears, although
not everyone (especially the elderly) will
hear to the extremes of this range.
20 000 +
Beyond normal hearing for humans,
although some animals (like dogs) hear
part ways into this range. Also used in
medicine (e.g. ultrasounds for pregnant
women).
LOUDNESS
• The system used to measure the loudness of sounds is the decibel system,
given the unit dB.
TONE
• Tone depends on the regularity of a
sound vibration. A simple tone has only
one frequency.. The tone of lowest
frequency is called the fundamental; the
others, overtones.
SPEED
• The speed of sound in
air depends on the
temperature of the air.
The speed of
sound is 340m/s at
15°C.
ECHO
• The echo depends on the
reflection of sound and its
return to the ear .
REVERBATION
• The reverberation of a sound
happens when the reflected soundwave returns to the ear in less than
0.1 seconds.
REFLECTION OF SOUND:
DOPPLER EFFECT
The Doppler effect can be
described as the effect
produced by a moving source
of waves in which there is an
apparent upward shift in
frequency for observers
towards whom the source is
approaching and an apparent
downward shift in frequency
for observers from whom the
source is receding.
SPECIFIC CONDUCT OF
LIGHT WAVES:
• Reflection.
• Diffusion.
• Refraction.
REFRACTION:
• Refraction is a phenomenon
that happens when an
incident ray hit a plane
separating two means. A part
of the ray is reflected, while
the other portion passes
through the second mean and
it looks deflected.
REFLECTION:
• Reflection is a phenomenon
that happens when a ray hit a
mirror.
LAWS OF REFRACTION:
• The first law of the refractions says that the incident ray, the refracted ray,
and the perpendicular line are in the same plane.
• The second law says that: (when α is the corner formed by the perpendicular
line with the incident ray and β is the corned formed by the perpendicular line
with the refracted ray) senα/senβ is a costant value.
LAWS OF REFLECTION:
• The first law of reflection says that the incident ray, the
reflective one, and the perpendicular line to the mirror are on
same plane.
• The incident ray and the reflective ray form with the
perpendicular line to the mirror two equal corners. This is the
second law of reflection.
DIFFUSION:
• Diffusion or scattering is a casual phenomenon and consists in a
deflection of light caused by the collision of the particles with other
particles.
COLOUR:
•The visible part of the electromagnetic
spectrum is called visible spectrum and
it’s composed by electromagnetic waves
with wavelenght between 380 – 760
nm.
• There are three fondamental colours:
red, blue and green. Superposing
fondamental colours, we gain all the
colours of the visible spectrum.
THE CALLING OF ST. MATTHEW
• This picture by Caravaggio is
drawn using dark colors and
stripes of lights, that illuminate
St. Matthew.
• The using of lights also gives to
observer the direction of picture
from right to left.
• The author decides to use light to
underline the call of God to
Matthew.
Glossary
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