Electromagnetic waves are a form of radiation
that travel though the universe.ii. Atomic Absorption Spectrum
When a beam of white light is passed through a gaseous sample of an element, the element takes
in certain wavelengths while the rest of wavelengths travel through it. The spectrum of this
radiation is called an atomic absorption spectrum.s
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The colors of the visible spectrum are violet, indigo, blue, green, orange, yellow and red and their
wavelengths vary from 400 nm to 750 nm. In addition to the visible region of the spectrum, there
are 7 other regions.FACULTY OF ENGINEERING - MTI UNIVERSITY 5 DR. ABDEL MAGIED DIAB
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Atomic spectrum can likewise be observed when elements in the gaseous state are heated at high
temperature or subjected to an electric discharge.i. Atomic emission spectrum
ii. Atomic absorption spectrum
i. Atomic Emission Spectrum
When solids are volatilized or elements in their gaseous states are heated to high temperature or
subjected to an electrical discharge, radiation of specific wavelengths are emitted.Electromagnetic radiation, in classical physics, the flow of energy at the universal speed of light
through free space or through a material medium in the form of the electric and magnetic fields
that make up electromagnetic waves such as radio waves, visible light, and gamma rays.FACULTY OF ENGINEERING - MTI UNIVERSITY 2 DR. ABDEL MAGIED DIAB
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A wave is a moving disturbance that transports energy from one place to another but does not
necessarily transport matter.Notice that the points on the strings (matter) do not
move horizontally
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Figure 1.(b) The crests and troughs are shown as waves when viewed from above
o wave front the continuous line or surface at the
start of a wave as it travels in time
o crest the upper part of a wave
o trough the lower part of a wave
o wavelength ? Both electricity and magnetism can be static (respectively, what holds a balloon to the wall or a
refrigerator magnet to metal), but when they change or move together, they make waves.In such
a wave, time-varying electric and magnetic fields are mutually linked with each other at right
angles and perpendicular to the direction of motion.Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves
to very short gamma rays.Ultraviolet, X-rays, ?-rays and cosmic rays
are towards the lower wavelength end of the
spectrum and they have the photons with
higher energies.Hence, a visual
display or dispersion of the components of
white light, when it is passed through a prism
is called a spectrum.o Types of Spectra
The spectrum of EM waves is of two types:
a) Continuous spectrum
b) Line spectrum
a) Continuous spectrum
In this kind of spectrum, the boundary line in between the colours cannot be marked.NASA's scientific instruments use the full range of the electromagnetic spectrum
to study the Earth, the solar system, and the universe beyond.On the other side of the
visible region, there lie infrared, microwave
and radio-frequency regions.b) Atomic or Line Spectrum
When an element or its compound is volatilized on a flame and the light released is seen through
a spectrometer.Similarly, the spectrum of hydrogen consists of a number of lines of different
colours having different distances from each other.An electromagnetic wave can also be described in terms of its
energy--in units of measure called electron volts (eV).Moving along the spectrum from long to
short wavelengths, energy increases as the wavelength shortens.For example, the line spectrum of sodium consists of 2 yellow coloured lines separated by a
definite distance.Magnetic
and electric fields of an electromagnetic wave are perpendicular to each other and to the direction
of the wave.An electromagnetic wave is characterized by
its intensity and the frequency ?The human eye can detect only a small portion of this spectrum called
visible light.More Intensity
or energy means shorter wavelength or higher frequencies.It is obtained from the light released by the sun or
incandescent (electrical light) solids.The wavelengths of the radiation that have
actually been absorbed by the element look like dark lines and the background are bright.1.1 red
arrows) couples with a magnetic field (Fig.1.1
blue arrows).of the time variation of the electric and magnetic fields.A radio detects a different portion of the spectrum, and an x-ray machine uses yet
another portion.When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven,
you are using electromagnetic energy.A periodic wave is a wave that
repeats itself at regular intervals.illustrates one way to generate a mechanical wave.In Figure 1.2(a), the per- son's hand
exerts a vertical force on the string, creating a wave pulse.(a) Wave pulse and (b) periodic waves along a string
Suppose that the person is shaking the string such that the string is moving in a periodic
fashion in the vertical direction.the distance between one positive
amplitude and the next
o phase the offset of the wave from a reference point.Two points on a wave that are at the same place in
a wave cycle (for example, two successive crests)
are said to have the same phase.o The period, T, of a wave is the time required for one wave cycle to pass a particular point, and
o the frequency, f, is the number of wave cycles that pass a particular point per unit of time.The
SI unit of frequency is the hertz, Hz. One hertz is equal to one cycle per second.n
1
f=
=
t
T
o The speed of a periodic wave is related to its frequency and wavelength.An electron
volt is the amount of kinetic energy needed to move an electron
through one volt potential.The very best
example of a continuous spectrum is rainbow.The spectrum
of this radiation contained bright lines against a dark background.They are
formed when an electric field (Fig.The simplest wave is a periodic wave.Since the force and the resulting pulse
act along the length of the string, the force does work on the string.In Figure 1.2 (b), as the hand
continues to move, the wave becomes periodic.The colours
diffuse into each other.It is the characteristic of matter in bulk.This kind of spectrum is called a
line spectrum or atomic spectrum.This is characteristic of an atom.There are two ways in which an atomic spectrum can be seen.This means that the wave
pulse carries energy along the string, from the hand to the wall.Figure 2 shows a snapshot of the wave as it begins to move
to the right.More
energy is needed to make the rope have more waves.One colour merges into another without any dark space.We see unique lines separated by dark areas.You depend on this energy every hour of every day.Without it, the world you know could not exist.Figure 1.2.Figure 1.2 (a) The wave moves to the right.