SPECTRUM

Spectrum

Introduction

A spectrum is a condition that is not limited to a specific set of values but can vary, without steps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colours in visible light after passing through a prism.  As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum.

In the 17th century, the word spectrum was introduced into optics by Isaac Newton, referring to the range of colours observed when white light was dispersed through a prism. Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot.

The term spectrum was expanded to apply to other waves, such as sound waves that could also be measured as a function of frequency, frequency spectrum and power spectrum of a signal.

Electromagnetic spectrum

Electromagnetic spectrum refers to the full range of all frequencies of electromagnetic radiation and also to the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object. Devices used to measure an electromagnetic spectrum are called ‘spectrograph’ or ‘spectrometer’. The visible spectrum is the part of the electromagnetic spectrum that can be seen by the human eye. The wavelength of visible light ranges from 390 to 700nm. The absorption spectrum of a chemical element or chemical compound is the spectrum of frequencies or wavelengths of incident radiation that are absorbed by the compound due to electron transitions from a lower to a higher energy state.

Light from many different sources contains various colours, each with its own brightness or intensity. A rainbow, or prism, sends these component colours in different directions, making them individually visible at different angles. A graph of the intensity plotted against the frequency is the frequency spectrum of the light. When all the visible frequencies are present equally, the perceived colour of the light is white, and the spectrum is a flat line.

In radio and telecommunications, the frequency spectrum can be shared among many different broadcasters. The radio spectrum is the part of the electromagnetic spectrum corresponding to frequencies lower below 300 GHz, which corresponds to wavelengths longer than about 1 mm. The microwave spectrum corresponds to frequencies between 300 MHz (0.3 GHz) and 300 GHz and wavelengths between one meter and one millimeter.

Mass spectrum

A plot of ion abundance as a function of mass to charge ratio is called a mass spectrum. It can be produced by a mass spectrometer instrument. The mass spectrum can be used to determine the quantity and mass of atoms and molecules.

Energy spectrum

In physics, the energy spectrum of a particle is the number of particles or intensity of a particle beam as a function of particle energy. Examples of techniques that produce an energy spectrum are alpha particle spectroscopy, electron energy loss spectroscopy, and mass analyzed ion kinetic energy spectrometry.

Discrete spectrum

In physics, particularly in quantum mechanics, some differential operator have discrete spectra, with gaps between values. Common cases include the Hamiltonian and the angular momentum operator.

Spectrogram

In acoustics, a spectrogram is a visual representation of the frequency spectrum of sound as a function of time or another variable.   An apparatus used for recording and measuring spectra, especially as a method of analysis.

Splitting of white light

Light changes speed as it moves from one medium to another (for example, from air into the glass of the prism). This speed change causes the light to be refracted and to enter the new medium at a different angle. The degree of bending of the light's path depends on the angle that the incident beam of light makes with the surface, and on the ratio between the refractive indices of the two media. 

Light of different colours to  be refracted differently and to leave the prism at different angles, creating an effect similar to a rainbow. This can be used to separate a beam of white light into its constituent spectrum of colours.

Reference

·        Wikipedia

SUBMITTED BY: 

Ahallya K V

Akshatha G

Akhila K

Athira V

Amal George

CAN YOU HEAR ME?

CAN YOU HEAR ME?

The Magic called Sound

What is it like, when you accidentally press the mute button of your TV remote, while watching an electrifying cricket match? Even though you still can watch the match, you certainly lose interest in the game without sound. If this is so, then think of a time when the whole world will fall into a mute mode. No one can even contemplate a soundless world.

The world we survive is full of sound. The world we live in is full of sound. The chirping of birds, whistling of wind, roaring of animals, splashing of water- these are all parts of rhythms of nature. Not only natural sounds, but man- made sounds like the honking of horns too become an inevitable part of our lives. In short, man and sound are inseparable.

Sound is the music of life

Sound, in its simplest sense, is an energy made by vibrations.

When an object vibrates, it creates the movement in the air particles. These particles get in contact with others close to them, and make them vibrate too. As this continues, it becomes a bigger process, with more and more air particles bumping into each other. This movement creates what is known as sound waves. It keeps going until the object runs out of energy. We hear the sound when our ears are within the range of the vibrations.

The speed of sound

The speed of sound primarily depends on the medium through which the waves travel. For instance, sound waves travels faster in water, than in air. But in the medium of steel , it’s even faster . In an ideal gas, speed of sound depends only on its temperature and composition.

There are fixed rates for the speed of sound wave. In dry air at 20⁰C the speed of sound is 343 meters per second. Now takes the case of water. Here, sound travels four times faster, at an approximate rate of 1,484 m/s . But in solids like iron, it reaches around 5,120 m/s !

The speed of light is 2.99792458 x 10⁸m/s, almost 870,000 times faster than the speed of sound! This is the reason why you see lightning before you hear the thunder.

Why is it said that Super Sonic aircraft surpass the speed of sound?

Supersonic speed refers to a speed greater than that of sound. A bullet fired from a modern day gun is said to have this kind of speed. Another important example is the supersonic air craft. They are flights which travel faster than the sound that is audible to human ears.

An Indian example of Supersonic flight is the HAL Tejas, which is still in service.   

Star facts:-

·       Study of sound

Acoustics is the scientific study of sound waves.

·       Phobias

While ‘Acousticophobia’ refers to the fear of noise, ‘melophobia’ refers to the fear of music!

·       Smaller is louder

Smaller objects vibrate faster, creating higher frequency sounds. This is why the sound of your voice being higher than your father’s

·       New Science

Cymatics is a relatively younger branch of science that stu dies geometric forms created by Sound waves.

·       Loud Enough

Loudness depends on how loud or soft the sound is; it is measured in decibels (dB). It has been found that at 125dB, a sound becomes painful to human ears.

·       Healing Effect

One of the techniques that uses sound waves to heal wounds is the ‘MIST’ therapy.

Sound Level Meter

The Sound level meter, a hand held instrument with microphone, is commonly used tool for acoustic measurements.

·       Far- Reaching

It is said that whales communicate with each other underwater, their sound waves travel up to 800km.

Sound need medium to pass through

We know that, our Diwali crackers bursts with sound. But do we think such big explosions and collisions of the massive objects in space creates sound? Well, there are no sounds coming from them. The reason behind this strange phenomenon is that, there is no ‘medium’outside the the Earth to travel through. Air is not the only medium through which sound waves can travel. It can pass through liquid and solids too.

Hearing Range of animals varies greatly

As matter of fact, no two species of animals look alike,or behave alike.Similarly, the abilities and senses of animals vary too, from species to species.

One cannot expect a monkey to have the hearing ability of an elephant, nor can auditory ability between a marine mammal and terrestrial animal be compared. Generally, it is seen that larger animals hear and use low frequency sounds while smaller ones have with higher frequencies. However, there are always exceptions, as in the case of spadefoot toads that can easily pick up low frequency sounds. These animals live in desert habitats.

Similar to animals, birds and insects too have peculiar auditory features that help them adapt to surroundings.

Birds are known for their musical communication

How many of us have seen birds that don’t make sounds? Not many. Birds are in fact, most known for their ability to make sound, be it sweet chirping, or harsh caws.

There are different frequencies at which birds’ sound come out . There are others too that can sing at high frequencies, like warblers, sparrows, waxwings, kinglet etc. It is believed that one can never stop a bird from learning its own species’ song.

Sound around us

What is Ultra sound?

We have heard that most humans can hear the sounds between 20 and 20000 hertz. Ultra sounds are above this limit, or specifically above 20000 Hz. They are not different rom normal sound in terms of physical properties. But the only difference is that they can be heard and produced by only a few animals like bat, moth,dolphins etc and not by humans. In other words, the range of ultrasound begins where our sonic range ends.

The uses of ultrasound can be seen in electronic, navigational, industrial, medicinal and security applications.

Ultra sounds are useful in SONAR

SONAR is the short form for SOund NAvigation and Ranging. It is an ultrasonic system used in ships and other vessels for navigation, and locating objects underwater.

As we know, Sound waves travel faster than light through water. However , ordinary sound waves cannot travel longer distances , only ultrasonics waves can. Due to their high frequency and short wavelength, ultrasonic waves penetrate water to very long distances and it is this feature that is utilized in Sonar.

Fig. Illustration that shows the work of a SONAR

Ultrasounds are useful in medicine

Fig. Ultrasound scanning

Some of the important applications of ultrasonics can be seen in the field of medicine. Ultrasonography or ultrasonic scanning is one of it, which uses high frequency sound waves to produce images of internal organs, vessels and tissues. This type of scanning is used to diagnose the condition of organs such as liver, kidneys, gallbladder.

Then there is something called obstetric ultrasound. It is a technique used during pregnancy to create images of a baby inside the womb.

Another public health application of ultrasounds is dental care. It enables the equipment called ‘descalers’ to remove plaque from teeth.

Fig. Ultrasound Scanning machine

Noise, noise, everywhere

Noise pollution or Sound pollution refers to the term of excessive and troublesome sound that effects all living things on Earth. Commonly, noise is discussed in terms od decibels (dB), which is also the measure of loudness or intensity of sound. There are different kinds of noise around us today, and one of it is environmental noise. Roughly speaking, it is the accumulation of all the noise present in the specified environment

It is said that plants have the ability to control adverse effect caused by the noise pollution. Hence , grow more and more plants, thus we can stay healthy and present a beautiful , calm environment to our future.

SUBMITTED BY:

Thushara R B

Yogini E

Pradeep A

Sahana D

(Ist M Sc)

Reference:

TELL ME WHY?

JOURNAL- JUNE 2017

INTERNET

BEYOND THE BLUE

What is “Beyond the Blue”?

Stars have fascinated the people since ancient times, but wasn’t until the 20^th century that exploring space became possible. In recent decades we have sent astronauts to the moon, robotic space crafts to the outer reaches of the solar system and used the telescopes to peer across the vastness of the Universe. Exploring beyond the blue sky became a reality to the mankind.

Observing the skies

For centuries, astronomers have observed the heavens with their eyes alone or used simple telescopes that magnify the view. But the visible light we see is just one part of a much bigger spectrum of electromagnetic rays that reaches the earth from space. Stars and other objects also emit invisible radio waves, x-rays, infrared, and microwave rays. Modern telescopes can see all of these, and each type of radiation reveals something different.

Capturing the light

Telescopes come in many different styles and designs, but basically all do the same thing: collect electromagnetic radiation from space and focus it to create an image. Earth’s atmosphere can block or blur the image, so some telescopes are located on high mountain tops or even launched into space. Some known telescopes among them are;

Radio telescopes : Huge, curved dishes are used to focus radio waves  given out by sources such as galaxies, pulsars and black holes

Microwave telescopes : Microwaves are short radio waves. By capturing these rays, telescopes can see ancient radiation from the Big bang.                          

Optical telescopes : Using large lenses or mirrors, optical telescopes gather faint visible light and can see much further than the human eye.

Infrared telescopes : These instruments, some of them are sent into space, detect the heat from the objects such as clouds of gas and dust. 

Mapping the stars    

Because Earth is surrounded by space, when we look at the night sky it seems as though all the stars are pinned  to the inside of a gaint sphere. Astronomers call this a celestial sphere and use it to map the positions of stars and planets. Vertical and horizontal lines are used to divide the celestial sphere into a grid, just like the grid of latitude and logitude lines used to map the Earth’s surface. Some among them are,

1.        Celestial north pole- This is the point directly above the north pole.

2.       Celestial south pole- This is the point directly above the south pole.

3.       Declination line- These split the sky into north south segments.

4.       Right ascension lines- These divide the sky into east west segments.

5.       Celestial equator- This imaginary line over the equator divides the sky into  
       north south hemispheres.

Exploring the planets

The planets are too far for manned missions, so robotic spacecrafts are sent instead. The first visit to another planet was made by ‘Mariner 2’, a US craft that flew past Venus in 1962. Since then, and despite number of failures, hundreds of spacecrafts have visited the solar system’s planets, moons, asteroids and comets. Most spacecrafts either fly past or orbit their target, but some also release landers that touch down on the surface.

An ORBITER is the one which flies around a planet repeatedly giving it plenty of time to study its target. Orbiters have visited the moon and all the planet except Uranus and Neptune.

A  PENETRATOR  is one which is designed to hit its target at high speed and bury itself. In 2005, satellite ‘Deep impact’ penetrated the surface of a comet.

A ROVER is a robotic lander with wheels that can drive about. Rovers sent to mars have studied its rocks for signs  of ancient life.

12 years and 43 days- the time it took the spacecraft ‘Voyager 2’ to reach Neptune from Earth.

Parts of a satellite.. 

• 1      Ultraviolet sensor
• 2       Generator
• 3       Magnetometer
• 4       Infrared sensor
• 5       Communication dish
• 6       Asteroid detector

 Launch vehicles                                                                                         

     

Space is only 100 km above earth’s surface and takes less than 10 minutes to reach in a rocket. Although the journey is short, it takes tremendous power to escape the pull of earth’s gravity. Launch vehicles are built to make the journey only one time, and most of their weight is fuel

World’s largest rockets

Saturn V, which sent astronauts to the moon was the largest rocket ever built. Some large rockets are..

     Delta heavy-72m

  

             Saturn V  -111m and N1-105m       

Long march 2F-62m

Arine 4-59m

Launch sites

Many countries have space flight launch sites. Sites closer to the equator can launch heavier cargo, because rockets are given a boost by the speed of Earth’s spin.

                                                            Major launch sites. 

Living in space

Astronauts must adapt to a zero gravity environment when living in space. Although floating weightlessly can be fun, it can also cause medical problems. Space stations are cramped places with few luxuries. Astronauts eat ready-made food that are either freeze-dried or served in pouches. All waters are recycled, including water vapour from human breath. Astronauts clean themselves with special shampoos and soaps that don’t need water, and they use space toilets that suck away waste rather than flushing with water.

Effects on the body

When the human body spend a long time in space, it changes. Without gravity pulling the spine, the body gets about 5cm taller. Body fluids that flow downwards on earth build up in head. This gives astronauts swollen faces and blocked noses, making food seem tasteless. When astronauts come back to the earth, the return of gravity can make them feel extremely weak

• Brain and balance: Without gravity, the inner ear’s balance system no longer works which can make astronauts sick.

• Muscles: Movement is easy when you are weightless, and muscles waste away if not used. Workout in on-board gym help to stop this happening.

• Bones: Bones weaken and become less dense. Regular excersice is essential to keep them strong.

Conclusion:

Space exploration has given us new technologies and now inspires new ideas for the program. Even though it has many good effects, the exploration contributes to global warming, there are ozone depleting substances and man-made debris in the earth orbit which must be controlled. Explorers and scientists are trying to sort out the problems of pollution and effects of harm nowadays.

SUBMITTED BY:

SHAYANA

SUJITH

LALAN

THILAKA

1st M.Sc {1st Semester} 

REFERENCE:     

Internet

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