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Simple Science - 2M ago

Our cosmos journey begins about billions of years ago when a hypothetical particles named 'singularity' begins to expand vigorously. Scientists said that, that expansion is caused due to the weird and unknown force which is known as 'Dark Energy'. Which is present everywhere in this universe. Singularity was a particle having infinity mass and infinity temperature, which was much smaller than the nucleus of an atom. It was floating in nothingness, nothingness means a hypothetical place where is no mass, no light, no energy even there is no space and time. As we have described that time make comparison between objects and events in this universe, but the singularity was something where all the thing is squeezed. So we can say that there is no flow of time. But here is a question- Why singularity was there? Unfortunately we can't answer.
Once singularity start expanding then it start creating space, energy, mass, light and so on. Singularity start expanding billions of years ago and it keeps expanding during this time, since you have started to read this sentence from that time to know it expanded about millions of kilometers. If universe is expanding then we can say the distance between objects in this universe is also expanding. Then why they stick together?
The expansion of the universe doesn't increase the distance between objects in this universe because, there are three forces in this universe which keeps matter in their shape, size, volume and place.
And those forces are:
1. Gravity
2. Electromagnetism
3. Strong Interaction

So, first we talk about the weakest force which is keeps you to stick with earth. And that force is 'Gravity'. As you know that the universe is expanding, but due to the gravitational force the distance between two objects like the sun and the earth remains unchanged. This force also keeps planets and moons in their orbit. It can be explain in better way, suppose that you and your friend are standing on a balloon which is inflating. With the enlargement of the balloon surface you will be noticed that the distance between you and your friend is increasing. But if you grab each other's hand then it will stop, so gravity works as same to keep to keep the distance between any two objects in this universe as same.
But distance can be increase if dark energy becomes more powerful than the gravity as it was at beginning. At that time, all the objects starts moving away from each other. All the planets, moon will go far apart.

And the second is electromagnetism, which is the second most powerful force in this universe. Which keeps atoms, elements and molecules in shape. If the dark energy goes beyond the electromagnetism then, the all atoms, elements and molecules will be scattered in to electrons and group of protons which is nucleus of an atom. There will be no any stuff in this universe. As we know that the electromagnetism is the force which keeps electrons to orbit the nucleus so, if there is no electromagnetism then no electrons will orbit the nucleus then there is no atom and if there is no atoms means no any stuff. Because any stuff in this universe is compost of atoms.

And the third one is the strongest force in this universe which keeps protons in a atom to be combined with each other. That force is 'Strong Intraction'. As this force hold protons in nucleus to be combined but, if the dark energy becomes more than strong interaction then all the protons in the nucleus scattered and all the universe contains only quarks.

But the dark energy is not strong enough at this time to beat these forces.
After the expansion of the cosmos there is a great role of these forces. Firstly the strong interaction combine the protons to make nucleus, then electromagnetism makes electrons to orbit the nucleus which to formation of the atom then after elements and finally molecules which further combined to form stuff. And the final touch is given by the gravity which start attracting more and more stuff to make huge bodies. The gravity also makes planets to orbit the sun, and moons to orbit planets.

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Simple Science - 2M ago

Today I am going to describe you about the red shift and blue shift of the white light. You are not going to see this phenomenon until you travel at the speed near the speed of light or until you see any object moving near the speed of light.

But you can experience the same phenomenon with sound. Have you ever heard the sound of vehicle sieren when it is moving towards you or moving away from you at high speed. You will noticed that when it is coming towards, then you will hear same sound with high pitch, but when it is going away from you then you will hear low pitch sound.

Well, why it happens?

As we know sound travels in the form of wave. When the vehicle is coming towards you, at that time the sound wave compresses, due to that compression of sound wave the wave-length of the sound wave get decrease due to which frequency get increased. But there is no change in its amplitude. ( It means 'db' remains constant ).

Similarly when vehicle is going away from you, then the sound wave get stretched due to which wave-length get get increase and frequency get decreased.

Come on the topic

Red shift: It is called as red shift because in this condition light coming from a source start looking red. When an object is moving away from an observer with the speed near the speed of light, then the electromagnetic wave (or light) start stretching ( not actually ) or its wave-length start increasing due to which it start looking red. Because when wave-length increases then frequency decreases. And as we know red light have low frequency and higher wave-length. So, it start looking red.

Blue shift: It is called as blue shift because in this condition light coming from a source start looking blue. When an object is moving towards an observer with the speed near the speed of light, then the electromagnetic wave (or light) start squeezing ( not actually ) or its wave-length start decreasing due to which it start looking blue. Because when wave-length decreases then frequency increases. And as we know blue light have high frequency and lower wave-length. So, it start looking blue.

How can we use this information.

When we see any blue light emitting body which is moving in space then we can say that, it is comming towards us. And when we see any red light emitting body which is moving in space then we can say that, it is going away from us.
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Simple Science - 2M ago
What happen when you put ice cubes in water? Is it sink or float? You have observed that the ice cubes remains just down to the surface instead of sinking. Do you know whats the reason behind it?
So, here is the answer. Water is a liquid substance which is formed up of hydrogen and oxygen molecules. When two hydrogen atom combine with one oxygen atom then it form a molecule of water. When water is in liquid state, the molecules of water have much kinetic energy due to which they remain moving here and there. Their molecules sliding over others, due which the space between molecules of water is very less. And as the space is less, so the density is much. But when the temperature of water goes down, then the kinetic energy of molecules also goes down and when temperature goes below 4℃, then the kinetic energy of the molecules becomes so less. At that time ice molecules have not enough kinetic energy to break the bond and move freely. Wait.. what type of bond does ice molecules have? The structure of the bond is given in the figure below.

Image.1: Molecular structure of ice.

Water have oxygen and hydrogen atom which forms a hexagonal structure that contains lots of space between them. And due to these spaces ice have less density than water that's why ice float on water.

This is same, when you put card in deck then it will take less space and also it have high density, but when you make card tower then it will take much space and also density will goes down.

Following experiment will show you, what happen when we freeze water.

Step 1- Fill a bottle up to the neck and seal its cap tightly.

Step 2- Put it in your freezer for 2 hours.

Step 3- Take out the bottle (when water inside it frozen completely) and keep it outside the freezer for 10 minutes or until you see the outer surface of ice melted.

Step 4- Open the cap slowly.

Observation: You will find that water start coming out with force for few minutes.

Conclusion: As you filled the bottle with water up to neck, but after freezing it start coming out. This phenomenon is occurred because as I described you above that ice molecules have a hexagonal structure which contains much of space in comparison to water molecules. That's why 1 kg of ice have much volume than 1 kg of water.

Thanks for visiting.
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Simple Science - 2M ago

But have you ever thought about the main motive of our life. Well it is a confusing question. Go beyond your limits and try to think about the motive of that organism, who developed first on this planet. At that time the climate of the earth was very harsh, so we can suppose their first motive were to survive. And for its survival, it is also necessary to maintain their body. But one day its body will give up die. To keep their existence they have to reproduce themselves. In this way they live forever. Not their body, but their gene. And the process of copying their DNA and forming a new organism is combined called as reproduction. This process is further divided into two types, sexual reproduction and asexual reproduction. In asexual reproduction offspring so formed by reproduction process are exact copy of their parent. Because their traits are coming from a single parent. But this process becomes much more complex in terms of sexual. In sexual reproduction offspring are/is not the exact copy of their parents. Because in sexual reproduction gametes are involved. ( Gamet is a special kind of cell which allow transmission of traits and having only half of a complete set of chromosomes.) So offspring have character of dominant. Well, come on topic.

Take a moment and think about yourself, who are you, where are you from and where are you inside your body. Is your body is yours or you are just forced to be in your body. These questions have no answer. Well we can say that the main motive of our life is to survive as long as possible, spread own gene as much as possible, and wait for death. We can say that we are just a slave of our own gene, who wants to live forever. Our gene just change bodies from bodies and tries to live as long as possible.

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Simple Science - 2M ago
We see the sun in the sky everyday, it's color is red when it is rising or setting and it's colour became bright white at noon. This happens due to the passing of sun rays through different atmosphere, and angle.
Sun is the closest star to the earth, it's size is equals to 400× size of the earth.
You see the sun everyday, but you have ever imagined, how sun is important to you or us? And what happens when there is no sun in sky?

Importance of sun is not little, it is too much that we can't imagine at a time. So just find the importance of sun by reading this post.

1. So, the first of all sun is essential for the growth of plant. If there is no plant on earth means there no animals on earth because plants are primary consumers which converts the raw into food by the process known as 'Photosynthesis'. Here is the formula: 6H2O + 6CO2 + Energy (sunlight) = C6 H12 O6+ + O2. As you seen in the following reaction, it forms Glucose (C6 H12 O6) + Oxygen (O2).

Which is used by animals to form energy.
C6 H12 O6 + O6 = Energy + 6CO2 + H2O
In this way energy circulated again and again. You have heard about food chain, this shows how organisms are interdependent on each other for food. Lets see the very simple example of food chain: Grass is eaten by deer and deer is eaten by Lion and when lion died the body of lion is eaten by wolf, eagle or many animals even microorganisms, when microorganisms decompose the boy it produces methane,CO2 and other gases which will dissolve in atmosphere, and the remaining part will dissolve in soil and again it is used by plants. And again deer will eat and same process will repeat.

2. Second importance is sun rays is also responsible for formation of Ozone layer over the earth. Ozone layer is protective gaseous layer over the earth which skips the UV rays of the sun to enter inside the biosphere of the earth.

O2 + UV ray forms 2O
And
O + O2 forms O3 (Ozone gas)

3. The third one is " Transportation of water all over the earth surfaces ". Sun is also responsible for distributing the water all over the earth. You have heard about water cycle, when Ice caps and glacier melts due to the Sun light it converted into small stream which goes down and down from hill and form a river. And river collects those water throughout the place where it goes and finally it fell in the sea. And again when sun light warmed up the sea and ocean water, then it converted into vapour and goes up and up and forms cloud by the process known as condensation, because there is low temperature at that height the condenced water again converted into water and fell on earth in the form of rain and snow and sometimes times ice also. Rain water which fell in cities and villages or any other areas is collected by drainage system which is connected to river. Freezing and melting of the glaciers is due to the revolution of the earth, which cause the changing of seasons on the earth. But here a new question arise, How those clouds transported to different regions? You will got the answer of this question in the next point.

4. Sun rays are also responsible for blowing of winds. When air of a place becomes warm due to sunlight it rays up because it becomes lighter than the air of place where is temperature is less in comparison to this place. The area near the sea have less temperature because water heated up late than earth, and water cooled down late than earth. This is cause of sea breeze during day and land breeze during night. When air rises up as you know when we goes up and up over earth surface then temperature will go decrease, that's why some air which rised up due to sun rays again came down due to gravity and again light air will goes up.
With the following points, we can say that their is a great importance of sun to complete every cycle of life on earth.

Need of sunlight in man-made appliances. If I say their is no light on earth if their is no sun. Then many people say, 'no I have worlds brightest flash light or electricity. But you really thinks without sunlight these energy will last long for a long time. Well it is not possible because we have not very much resource on our planet. As you know that hydroelectricity is the biggest source of electricity for us, we cannot generate it without water. But How electricity forms with water? And answer is ' When water is collected in dam, collected water possess high potential energy and when it flow through narrow path it possess high thrust, and water with high thrust rotate the dynmo motor rapidly which leads in formation of electricity and as it is generated by using the power of water that's why it is called 'Hydroelectricity'.

But still we doesn't found the use of sunlight in formation of hydroelectricity. As you know circulation of water on earth is made by sunlight, if there is no sun then there is no circulation of water on earth, and if there is no circulation of water on earth then there is not ang river on earth, and without river there is not any dam, then how we will generate electricity? But still there is one more way to generate electricity. We can rotate the dynmo motors with the help of fossil fuels engine, but did you know there is very few fossil fuels are lefting on earth. Scientists predicted it will maximum last long for next 80 years, if we use it as, we are using it right now and if there is no sun then the use of fossil fuels will increase by more than 50× then it will end in very less time.
Nuclear fission can help us during that condition.
But don't think much more, if there is no sun, then whole earth will freeze down and then their is no life on earth and their is no any matter for finding other resources. Also our Earth will loose it's orbit and will lost in this universe.

This is a short note, which tells us about the importance of sun, if you like this post then please share this post with your family and friends and keep visiting our site.
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Simple Science - 2M ago

We see various life forms all around us, everyone of them have their differences and also some similarity. But the processes which are occurring inside their body for their survival are same, whether their organs are different. There is also a huge number of life forms around us which we can't able to see with our naked eyes. Yes! I'm talking about microorganisms. Scientists believe that the first living organism on the earth was a microorganism which have not a well defined cell ( they also called as prokaryotic cells ). After several genetic mutation those prokaryotic celled organism came in the form of eukaryotes and then after multicellular and they also becomes huge organisms with very much complicated body. But the phenomena is not very simple.
About 3.8 billion years ago when the temperature of the earth suddenly goes down to below 100℃ which makes the vapours ( gaseous H2O ) to water ( liquid H2O ) and at that time a great monsoon come over the whole earth. Which give the birth of several oceans and the blue colour of our planet. In those early oceans, the most strangest event occurred in the history of the earth, which led to the formation of the first organism on the earth. But still nobody knows, how those primitive organisms were able to survive in that extreme condition. This shows that the primitive organisms were much more developed than the organisms in today's world. That is why we still can't able to define that first organism. And how such complicated organism developed by itself.
Today we know that the terrestrial life form is based on organic compounds for example: your body is made up of an organic compound named ' Amino acid'. But the problem is that, protiens in today's organisms are incredibly complicated. Some of them are compost of hundreds of aminoacids which is arranged in a precise manner. This is impossible to believe that such complicated compounds were form by itself. So, there is no any organism on the earth which is developed by its own, they must evolved from other.
But what leads the early elements to build an organic compound which can do several life processes? And how that looks like? Unfortunately nobody knows. Possibly it was just a simple molecule, but that molecule differed from others because it have ability to make copy of its own. But scientists believe that they have a RNA or ribonucleic acid but even that is fairly complicated to be created by any accident.
Whatever the case, this first replicating compound was eventually replaced by DNA ( Deoxyribonucleic acid ). It wrapped itself into a protective shell ( called as 'cell wall' ) which leads the formation of the first prokaryotic cell on the earth which was similar to today's prokaryotic cells. DNA determines the exact appearance of every living organism. The protective cell of your immune system vigilantly look for unwanted visitor, growing of your nail, hair and height these all were determines by your DNA.

Reproduction

To reproduce offspring primitive organism copy its DNA in to a new shell by breaking its body in to two parts. But modern complicated organisms achieve that by sexual reproduction. In this type of reproduction two individual decide to join their DNA into one. Which makes their offspring a quite different from them. But prokaryotic cells reproduce by dividing itself as I mentioned above. Imagine, suddenly your body cut down into two and form two organisms. This type of reproduction were done by early cells and today's also. This process is categories in to asexual reproduction and also several ways of reproduction came under this for example: budding, fragmentation etc.
As I've described that during reproduction an organism copy its DNA to offspring. But this process is not perfect every time. There were several errors may be done during copying the DNA. A disobedient particle inside DNA finds itself in a wrong place or a certain segment of DNA is copied multiple times. These errors are called 'Genetic Mutation'. This phenomena had played a great role in evolution. Due to genetic mutation the offspring of an organism can becomes abnormal but some times these abnormality becomes a new quality of the organism and that quality again goes to the next offspring. These quality may be - better digestion, immediately, sensation, etc. Due to those genetic mutation prokaryotic cells finally becomes eukaryotic cells which have a well defined organelle.

Eukaryotic to multicellular

About 1.2 billion years ago some eukaryotic cells decided to join themselves in a ordered manners and become a complex unit and this event gave birth to the multicellular organisms on the earth. Then after 600 million years the amount of oxygen in the atmosphere raised. As result of it a sheet of ozone gas formed over the atmosphere of the earth. And now aquatic animals can come on land because their is no ultraviolet rays are falling on the earth surfaces and also their is a huge amount of oxygen on earth surfaces in comparison to in water. Thereafter 100 million years, the first plant, animal and fungi appeared. Then the formation of much complicated organisms were started. And finally the whole earth filled with small fishes, sharks, beetles, etc. 270 million years later the dinosaurs becomes the most dominant species on the earth at that time. With a monster sized body and full of strength they lead whole earth. But 65 million years ago, an event occurred that changed everything. A huge meteorite of radius 10 km striked the earth in today's mexico that cause the ultimate downfall of dinasour.
To be continued.... In another post.

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Simple Science - 2M ago

We see dreams every night, it may be scary or beautiful. While dreaming we see several indescribable thing like you just changed your place suddenly or suddenly you fell in a pit or from a building.  But why we see weird thing inside our dreams? Answer is, our mind have very much curiosity to know what happen if I do this or that. So our brain need a world where it can perform various experiment and know the result of it. So, we can say that our dreams are experimental world where our brain do experiments. And as we know experiments may be weird. And we can also define it as,
Dreaming is a normal thinking but difference is that during thinking this (dreams), we have no our control on our brain. From here we can say that, we think our dreams, but some people use to say that he/she see their dreams.

Do you think that there is any importance of dreaming on our life?
If your answer is yes? Then you are absolutely right, because there are several inventions and discovery which directly or indirectly came from dreams. For example:  Theory of relativity, Structure of DNA, Tubelight etc. Einstein told that, he always revise their theories which were unsolved, so he can dream about that. In this way we got the theory of relativity.

Dreaming is also important for our mind because through dreaming our mind can achieve relaxation.

There are a number of different theories on dreaming and their explanation. Sigmund Freud referred to dreams as being the royal road to the unconscious. He believed they held huge significance to our unconscious thoughts and feelings. In our busy day we can have a tendency to push into the depths of our minds, those thoughts, feelings and ideas which disturb, shock or worry us the most. However, our unconscious mind is not a locked vault and nothing we place there is ever truly hidden from view. These difficult and distressing thoughts and ideas often have a way of showing themselves in a variety of different ways, such as through our dreams. Means our dreams may be determined our unconscious mind.

Why do we dream

Well there is not any appropriate reason for dreaming but studies tells that during sleeping, our brain make several connections which leads a huge neurological activity and that cause dreaming.

This is not the end.
We will expand this post soon as possible.
Thanks for coming.
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Simple Science - 2M ago

We have heard many times, Atom bombs are very destructive weapon made by mankind. It is one of the baddest invention ever, it may be best invention for war lover. These bombs have power to make a city in to barren in just few seconds. There is very few country in this world which have this bomb, Like USA, UK, Soviet Union (Russia), France, China, India, Pakistan and North Korea. Atom bombs have been used twice in a war, both times USA used against Japan near the end of second world war on the the 6th of August 1945. By the using this bomb US won over the Japan when Japanese give up after the massive destruction caused by Atom bombs in 'Hiroshima' and 'Nagasaki'. About 100,000 Japanese died after this move of USA. It was the first and the last use of Atom bombs in a war.

The weight of Atom bombs are 10,300 pounds (about 5000kg) but when or blasts, or create energy which is equals to the energy created by blast of 20,000 tons of TNT. The weight of a Atom bomb is not more than the weight of a average petrol tanker but when both will blast, there is a massive differences between their energy output.

Why this happens?

Did you remember the formula which tells mass and energy are interchangeable? Yes, I am talking about " E=MC^2". This formula is given by Albert Einstein in 1905. In this formula E= Energy, M= Mass and C= Speed of light ( that is about 186,000 miles/sec ). By giving this formula Einstein change the way of peoples to think about mass and energy. E=MC^2 for the first time connected the mass of an object with its energy and hearled a new world of physics.
With this formula if we calculate the energy posses by 1 kg of mass is equals to 9×10^16 joules, if we somehow transform all of it into energy. This amount of energy is capable to light 10 million houses for at least 4 years. So, if we take 100 kg and convert it directly into energy then we can light 10 million houses for 400 years, means 4 century. Unfortunately, it is not a easy task but this is a very hard task, however nuclear fission is one of several ways to release a little bit of energy from a mass, but most of the stuff remains in the form of familiar protons, neutrons and electrons. One more way to convert an entire block of matter into pure energy would be to bring it together with antimatter particles of matter and antimatter are same, expect for an opposite electrical charge. Unfortunately, we don't know any natural source of antimatter, the only way to produce it, is in particle accelerators and it would be take up to 10 million years to produce a kilogram of it. Then which method is use in an Atom bomb?
An Atom bomb use fission reaction to convert about 10% of mass into energy. The energy of Atom bomb came from nucleus of atom, just it does with fission weapon (Atom bombs). In Atom bombs, a mass of fissile material ( Material which is rich in uranium or plutonium ) if forced into supercriticality- allowing on exponential by shooting one piece of subcritical material in to another (this is also known as "Gun" method)

Amount of energy produces when an Atom bomb blast:

● Blast- 40-50% of total amount of energy.
● Ionizing radiation- 5% of total amount of energy.
● Thermal radiation- 30-50% of total amount of energy.
● Residual radiation- 5-10% of total amount of energy.

What happens when an Atom bomb blast?

● When an Atom bomb blast it produce a vaccum area just above the blast place.
● A mushroom like structure of cloud,smoke,dust forms above the blast place, which height is about 20km.
● Very high shock wave produces, which is much more than any natural earthquake ( which is enough to turn any city in barren )
● Too much ionizing radiation forms which last long for several years.
● Too much bright which is enough to burn a concrete wall fully, it makes any creature on earth blind by just seeing it.

What I think about Atom bomb?
> I think this is the baddest invention ever made by humans. This is misuse of science and technology. We are human, we all are human, then how someone kill his/her own species. Not only humans all animals on this planet are interconnected with each other. If we use this energy as electricity for lighting our houses then we have enough for far 10000 years. This is nothing more than the wastage of energy. Day by day we are going to empty our fossil fuels. In this condition we don't have to waste our energy. If don't have any idea about destruction cause by Atom bomb then must search on Google about the atom bomb blast in Japan.

Hope you enjoyed this.
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Simple Science - 2M ago

Our whole earth is full of life, whether you go deep inside ocean or up above mountains or where you are, You will find life. Even when you are taking a bite of your bread you are eating a huge colony of microorganisms. Your hand, your bed, your body, your clothes all these are covered with a huge colony of microorganisms.
Scientists contributed that, there are millions of living organisms living on the earth. But we only know about 1 millions of them.
So, come on the topic. The main question is that what is life and how it came into existence. Many people thinks that life is started with magic. But they really think about magic in this era of science and technology. But still science can not able to explain everything about the starting of life. But life is same as all the thing in this universe, means it must obey the laws of the universe. Organisms are just a collection of molecules arranged in a unique way which make an organism functional. When we go deep and study about the function of a cell then we found how it obey the laws of the universe.
Darwin's theory of evolution tells about how life evolved from a single cell (unicellular) organism to multicellular organism. And the Mendel's experiment tells us about the mechanism of inheriting the traits from one generation to next generation. But none of them could able to explain about the beginning of the life on the earth.
Then, J.B.S. Haldane, a British scientist, suggested that life originated from the simple inorganic molecules such as ammonia, methane and hydrogen sulphide which were present on the earth soon after it was formed. It is known as the 'naturalistic theory' or ' The theory of chemical origin of life. It states that the conditions on the earth at that time could have transformed simple inorganic molecules into complex organic molecules they were necessary for life. But Haldane only suggested this phenomena.
Finally, Stanley L. Miller and Harold C. Urey in 1953 confirmed the theory of life proposed by Haldane. And this experiment is known as 'Miller and Urey experiment.
● Miller and Urey assembled an apparatus by creating an atmosphere that was similar to the early atmosphere on the earth.
● The apparatus consisted of gases like methane, ammonia and hydrogen sulphide but no oxygen over water.
● The apparatus was maintained at a temperature just below the 100℃ and electric spark were passes through the mixture of gases to simulate lighting.
● Finally, at the end of a week, 15% of the carbon (from methane- CH4 ) had been converted to simple carbon compounds including amino acids made up of protein molecules in living organisms.
Finally, the experiment provided the evidence that the life originated from the inorganic molecules.

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Simple Science - 2M ago

Light is what which makes us to see this beautiful world. When light strike any surface it immediately reverse back which came into our eyes and make us to see. Light is present everywhere in this universe either it is in form of infrared, ultrarays or any other. But we only see the light which fall under 400 to 700 NM wavelength. The different colours which we see it is due to the various frequency of light. ROYGBIV these text indicates the ascending order of frequency of light.
R for Red
O for Orange
Y for Yellow
G for Green
B for Blue
I for Indigo
V for Violet

Light is a form of energy which produces when electron of an atom goes down or closer to the nucleus by loosing some energy. So we can say that, when electron of an element loses its energy in the form of electromagnetic waves and those waves are light. Light is a electromagnetic wave consisting of electric and magnetic waves and both of them are perpendicular to each other.
Light which is visible to human eyes, lies between infrared and ultraviolet rays or the light which the wavelength range between 400-700 NM (nano-meters). Here you will ask " Is light wave? ". Actually light behaves as wave-particle duality. It means it have property of both particle as well as wave. Every substance in this universe have both properties, as the size of substance increases the wave properties of the substance get decreases and as the size decreases the wave property increases. Light may be visible or not for example: gamma rays, X-rays, microwaves and radio waves are also light but their frequency does not lies between the visible frequency of human eyes so it is not visible. Like all types of EM radiation (EMR) visible light propagates as waves. However, the energy imparted by the way particles are absorbed and absorbed energy of EM waves is called a photon.
EMR in of visible light consist quanta (photon) that are at the lower end of the energies that are capable of causing electronic excitation within molecules which leads to change in the bonding or chemistry of any molecule.

Light plays a great role since the life started on earth, sunlight which trapped by plant converted into chemical energy. And the energy utilize for splitting the Water molecules into hydrogen and oxygen which take part in photosynthesis and form glucose molecules. Plant utilize those glucose molecules for their survival and remaining store in form of fruits. Herbivores organism utilize those fruit for their survival and herbivores utilize by carnivores.
The primary properties of visible light are intensity, propagation direction, polarization and frequency. The speed of light (about 300,000 km/s) is one of the fundamental constant of nature.
Units and measurements of light:
Light is measure with two main units:
1. Radiometry- It measure the wavelengths of light.
2. It measures the wavelength weighted with respect to a standardized model of human brightness perception.

History of light

From begining, light was the one of the topic which ends the thinking of human. But the well known physicist Isaac Newton proposed corpuscles theory of light. According to this theory, light consist of small invisible particles called corpuscles. These corpuscles were considered to be highly elastic in nature. This theory could successfully explain the phenomena of reflection and refraction of light, which was not limited because the corpuscles theory of light didn't explain the phenomena of diffraction of light.

Then after in 1678 a dutch physicist "Christian Hygains" proposed wave theory of light. According to his theory- light is longitudinal wave which required medium for their propagation. And he contributed a hypothetical medium "Ether" which is present everywhere in this cosmos.

Later on the existence of the "Ether" was furshified. But Hygone's wave theory could successfully explain the phenomena of reflection, refraction, diffraction and interference. Later on Thomas young in 1801 experimentally proved the Hygon's wave theory of light. But the phenomena like polarisation could not be explained on the basis of Hygon's wave theory.
Electromagnetic theory of light-
In the half of the 19th century, James Clerk Maxwell contributed the electromagnetic theory of light. According to this theory light is formed up of electric and magnetic fields which occilate simultaneously in the the direction perpendicular to each other. As you can see in the figure below.

Points about electromagnetic theory of light, which proved it true:

● Electromagnetic waves do not required any medium for their propagation.

● Electromagnetic waves travels fastest in vacuum (Speed about- 3×10^8 m/s)

And because both these characteristics of wave present in light so it led to the development of electromagnetic theory of light according to which light is an electromagnetic wave.
Electromagnetic theory of light could explain the phenomena of light except photoelectric effect.

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