TECHNOLOGY IN
SCIENCE
Sofia Cuevas
28/04/2014
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INDEX
LIGHT
P.3
SOUND
P.6
ENERGY
P.9
SOURCES
P.12
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LIGHT
An age-old debate that has persisted among scientists is related to the
question, "Is light a wave or a stream of particles?" Very noteworthy and
distinguished physicists have taken up each side of the argument, providing a
wealth of evidence for each side. The fact is that light exhibits behaviors that
are characteristic of both waves and particles.
Wave interference is a phenomenon that occurs when two waves meet while
traveling along the same medium. The interference of waves causes the
medium to take on a shape that results from the net effect of the two
individual waves upon the particles of the medium. Wave interference can be
constructive or destructive in nature. Constructive interference occurs at any
location along the medium where the two interfering waves have a
displacement in the same direction. For example, if at a given instant in time
and location along the medium, the crest of one wave meets the crest of a
second wave, they will interfere in such a manner as to produce a "supercrest." Similarly, the interference of a trough and a trough interfere
constructively to produce a "super-trough." Destructive interference occurs
at any location along the medium where the two interfering waves have a
displacement in the opposite direction. For example, the interference of a crest
with a trough is an example of destructive interference. Destructive
interference has the tendency to decrease the resulting amount of displacement
of the medium.
Perhaps you have witnessed streaks of color on a car windshield
shortly after it has been swiped by a windshield wiper or a squeegee at
a gas station. The momentary streaks of color are the result of
interference of light by the very thin film of water or soap that remains
on the windshield. Or perhaps you have witnessed streaks of color in a
thin film of oil resting upon a water puddle or concrete driveway.
These streaks of color are the result of the interference of light by the
very thin film of oil that is spread over the water surface. This form of
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interference is commonly called thin film interference and provides
another line of evidence for the wave behavior of light.
Einstein, though, is getting ahead of the story. To appreciate how light
works, we have to put it in its proper historical context. Our first stop is
the ancient world, where some of the earliest scientists and
philosophers pondered the true nature of this mysterious substance
that stimulates sight and makes things visible.
Visible light (commonly referred to simply as light) is electromagnetic
radiation that is visible to the human eye, and is responsible for the
sense of sight. Visible light is usually defined as having a wavelength in
the range of 400 nanometres (nm), or 400×10−9 m, to 700 nanometres
– between the infrared, with longer wavelengths and the ultraviolet,
with shorter wavelengths. These numbers do not represent the
absolute limits of human vision, but the approximate range within which
most people can see reasonably well under most circumstances.
Various sources define visible light as narrowly as 420 to 680 to as
broadly as 380 to 800 nm. Under ideal laboratory conditions, people
can see infrared up to at least 1050 nm, children and young adults
ultraviolet down to about 310 to 313 nm.
Primary properties of visible light are intensity, propagation
direction, frequency or wavelength spectrum, and polarisation,
INTESITY
In physics, intensity is the power transferred per unit area. In
the SI system, it has units watts per meter squared (W/m2). It is used
most frequently with waves, in which case the average power transfer
over one period of the wave is used. Intensity can be applied to other
circumstances where energy is transferred.
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FRECUENCY
Frequency is the number of occurrences of a repeating event per
unit time. It is also referred to as temporal frequency, which
emphasizes the contrast to spatial frequency and angular frequency.
The period is the duration of one cycle in a repeating event, so the
period is the reciprocal of the frequency.
POLARIZATION
The transverse nature of an electromagnetic wave is quite different from any
other type of wave. Let's suppose that we use the customary slinky to model
the behavior of an electromagnetic wave. As an electromagnetic wave
traveled towards you, then you would observe the vibrations of the slinky
occurring in more than one plane of vibration. This is quite different than
what you might notice if you were to look along a slinky and observe a slinky
wave traveling towards you. Indeed, the coils of the slinky would be vibrating
back and forth as the slinky approached; yet these vibrations would occur in
a single plane of space. That is, the coils of the slinky might vibrate up and
down or left and right. Yet regardless of their direction of vibration, they
would be moving along the same linear direction as you sighted along the
slinky.
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SOUND
Sound and music are parts of our everyday sensory experience. Just as humans
have eyes for the detection of light and color, so we are equipped with ears for the
detection of sound. We seldom take the time to ponder the characteristics and
behaviors of sound and the mechanisms by which sounds are produced,
propagated, and detected. The basis for an understanding of sound, music and
hearing is the physics of waves. Sound is a wave that is created by vibrating
objects and propagated through a medium from one location to another. In this
unit, we will investigate the nature, properties and behaviors of sound waves and
apply basic wave principles towards an understanding of music.
ACOUSTICS
Acoustics is the interdisciplinary science that deals with the study of all
mechanical waves in gases, liquids, and solids including vibration, sound,
ultrasound and infrasound. A scientist who works in the field of acoustics is
an acoustician while someone working in the field of acoustical
engineering may be called an acoustical engineer. (Not to be confused with
an audio engineer.) The application of acoustics can be seen in almost all
aspects of modern society, sub disciplines include: aero acoustics, audio
signal processing, architectural acoustics, bioacoustics, electro
acoustics, environmental noise, musical acoustics, noise
control, psychoacoustics, speech, ultrasound, underwater and vibration.
PROPAGATION OF SOUND
Sound propagates through compressible media such as air, water and solids
as longitudinal waves and also as a transverse waves in solids. The sound
waves are generated by a sound source, such as the vibrating diaphragm of
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a stereo speaker. The sound source creates vibrations in the surrounding
medium. As the source continues to vibrate the medium, the vibrations
propagate away from the source at the speed of sound, thus forming the
sound wave. At a fixed distance from the source, the pressure, velocity, and
displacement of the medium vary in time. At an instant in time, the pressure,
velocity, and displacement vary in space. Note that the particles of the
medium do not travel with the sound wave. This is intuitively obvious for a
solid, and the same is true for liquids and gases (that is, the vibrations of
particles in the gas or liquid transport the vibrations, while
the average position of the particles over time do not change). During
propagation, waves can be reflected, refracted, or attenuated by the
medium.
The behavior of sound propagation is generally affected by three things:
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A relationship between density and pressure. This relationship, affected
by temperature, determines the speed of sound within the medium.
The propagation is also affected by the motion of the medium itself. For
example, sound moving through wind. Independent of the motion of
sound through the medium, if the medium is moving, the sound is further
transported.
The viscosity of the medium also affects the motion of sound waves. It
determines the rate at which sound is attenuated. For many media, such
as air or water, attenuation due to viscosity is negligible.
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ENERGY
In physics, energy is a property of objects, transferable among them
via fundamental interactions, which can be converted in form but not
created or destroyed. The joule is the SI unit of energy, based on the
amount transferred to an object by the mechanical work of moving it
1 meter against a force of 1 newton.
Work and heat are two categories of processes or mechanisms that
can transfer a given amount of energy. The second law of
thermodynamics limits the amount of work that can be performed by
energy that is obtained via a heating process—some energy is always
lost as waste heat. The maximum amount that can go into work is
called the available energy. Systems such as machines and living
things often require available energy, not just any energy. Mechanical
and other forms of energy can be transformed in the other direction
into thermal energy without such limitations.
There are many forms of energy, but all these types must meet certain
conditions such as being convertible to other kinds of energy, obeying
conservation of energy, and causing a proportional change in mass in
objects that possess it. Common energy forms include the kinetic
energy of a moving object, the radiant energy carried by light and
other electromagnetic radiation, the potential energy stored by virtue of
the position of an object in a force field such as
a gravitational, electric or magnetic field, and the thermal
energy comprising the microscopic kinetic and potential energies of the
disordered motions of the particles making up matter. Some specific
forms of potential energy include elastic energy due to the stretching or
deformation of solid objects and chemical energy such as is released
when a fuel burns. Any object that has mass when stationary, such as
a piece of ordinary matter, is said to have rest mass, or
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an equivalent amount of energy whose form is called rest energy,
though this isn't immediately apparent in everyday phenomena
described by classical physics.
ENERGY TRANSFORMATION
Energy may be transformed between different forms at various efficiencies.
Items that transform between these forms are called transducers.
Energy transformations in the universe over time are characterized by
various kinds of potential energy that has been available since the Big Bang,
later being "released" (transformed to more active types of energy such as
kinetic or radiant energy), when a triggering mechanism is available. Familiar
examples of such processes include nuclear decay, in which energy is
released that was originally "stored" in heavy isotopes (such
as uranium and thorium), by nucleosynthesis, a process ultimately using the
gravitational potential energy released from the gravitational
collapse of supernovae, to store energy in the creation of these heavy
elements before they were incorporated into the solar system and the Earth.
This energy is triggered and released in nuclear fission bombs or in civil
nuclear power generation. Similarly, in the case of a chemical
explosion, chemical potential energy is transformed to kinetic
energy and thermal energy in a very short time. Yet another example is that
of a pendulum. At its highest points the kinetic energy is zero and the
gravitational is at maximum. At its lowest point the kinetic energy is at
maximum and is equal to the decrease of potential energy. If one
(unrealistically) assumes that there is no friction or other losses, the
conversion of energy between these processes would be perfect, and
the pendulum would continue swinging forever.
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SOURCES
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http://science.howstuffworks.com/light.htm
http://en.wikipedia.org/wiki/Light
http://en.wikipedia.org/wiki/Sound
http://en.wikipedia.org/wiki/Energy#Transformation
http://www.physicsclassroom.com/class/light/Lesson-1/Thin-FilmInterference
http://www.physicsclassroom.com/class/light/Lesson-1/Two-PointSource-Interference
http://www.physicsclassroom.com/class/light/Lesson-1/WavelikeBehaviors-of-Light
http://www.physicsclassroom.com/class/light
http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-is-aMechanical-Wave
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