Why Auroras emit 8 streams of coloured light?

Why Auroras emit 8 streams of coloured light?

PROF WAQAR HUSSAIN

             

     Aurora has literal meaning “sunrise”; Aurora is also name of Roman goddess of dawn. Aurora in Urdu is called Kutub raushani(light of poles).It is a luminous meteoric phenomenon of electrical character seen about 80 km above  Polar Regions with a tremulous motion and giving forth streams of eight Aurora or curly coloured dashing storm of light. This illumination of sky flowing from North Pole is called Aurora Borealis(Boreas means north wind) or Northern Lights, and streaming from South Pole is called Aurora Australis or

Southern Lights. They are actually caused by radiation from the sun-spots. A stream of electrons thrown out from the solar cyclone reaches the atmosphere of the earth and there strike the gases in the upper atmosphere, it causes them to vibrate, excite, glow and flow.

            Northern lights are caused by collisions of fast moving electrons (coming from space) with oxygen, nitrogen and other gas molecules present 

in our atmosphere. These electrons originate from the sun. The outermost surface of sun corona has temperature of 2 million ^oC and emits solar wind containing free electrons and positive ions. Solar wind reaches earth with speed of 400km/s and magnetic field of 2-5 nanoteslas. This speed and magnetic field increases several times during magnetic 

storm. Earth magnetosphere is formed by the impact of solar wind on earth magnetic field which blocks solar wind. Still some potion travel toward the poles.

               Electrons of solar wind collide with electrons of oxygen and nitrogen molecule. As a result, electrons of oxygen and nitrogen are excited i.e. they shift to high energy state or oxygen and nitrogen lose their own electrons to form ions. 

When excited electrons return to normal ground state, energy is released in the form of radiation of different colour and form aurora. Oxygen generally gives greenish –yellow or red light while nitrogen gives off blue light.

Why diamond glitters and gives white as well as coloured light?

Why diamond glitters and gives white as well as coloured light?

PROF WAQAR HUSSAIN

           

Diamond literal meaning unbreakable is an allotropic form of carbon with face-centered cubic structure called diamond lattice. It is the hardest known natural material with high optical dispersion (ability to disperse light of different colour), high refractive index (2.417), etc.

       

          Diamonds glitter due to total internal refraction (explanation is given below as 1) It is cut in a way to get number of faces so that if a ray of light enters in it, it must strike the face at an angle greater than its critical angle (for diamond it is approximately 24.4^o degree).When light strike a surface at angle greater then critical angle, it is reflected back instead of going out as refraction. Greater are the reflections, greater is the glitter. The brilliance also depends on the cutting pattern of a diamond .Greater are reflective surfaces, greater are reflections and in turn greater is glitter. So, its brilliance also depends on the diamond cutter's skill. It is the art of the lapidary, cutting numerous facets which enable the material to make the most of its reflective powers.

                  

         Or have another dimension of the above discussion. Diamonds have a high refractive index (explanation is given below as 2) which means that light travelling through them will be bent more than in any other substances. Bending of light is due to fact that the speed of light is slowed down in a diamond. When it hits the face, when the speed is drastically reduced, it tends to bend significantly. So, light instead of going out, it is reflected back and again it strike other face and is reflected and it strikes many times and meet the same fate. Finally it finds the way out either as white light or as band of seven colour. It is analogous to carrom board striker which when struck with full force; keep on striking different sides of carrom board. This entire phenomenon appears to observer as glitter. It is called an adamantine luster.

1) Total internal reflection. When, a beam of light passes from a denser to a rare medium, refracted ray bends away from the normal and the angle of refraction is greater than the corresponding angle of incidence. As the angle of incidence increases, the angle of refraction also increases till for a certain value of angle of incidence, the corresponding angle of refraction equal to 90⁰ .The angle of incidence for which the angle of refraction is 90⁰ is called the critical angle.

           When the value of angle of incidence becomes greater than the critical angle, the ray of light no longer suffers refraction but the whole of it, is reflected back in the denser medium. Such a reflection of light is called total internal reflection.

           Let’s have an analogous example, striker in carrom board shows total internal reflection.

2) Refractive index, also called index of refraction, measure of the bending of a ray of light when passing from one medium into another. If i is the angle of incidence of a ray in vacuum (angle between the incoming ray and the perpendicular to the surface of a medium, called the normal;  and r is the angle of refraction (angle between the ray in the medium and the normal), the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction; i.e., n = sin i / sin r. Refractive index is also equal to the velocity c of light of a given  wavelength in empty space divided by its velocity v in a substance, or n = c/v.( Encyclopedia Britannica)

          It is the measure of degree of speed of lessened in a material relative to speed of light in vacuum. Its high value indicates that the said material has reduced the speed of light to a greater extent.

Why flowers are brightly coloured?

Why flowers are brightly coloured?

PROF WAQAR HUSSAIN

            

The flowers contain pollen grains and inter-mixture of pollen is essential for reproduction of vegetation. Pollen is carried from one plant to another by bees and other insects which move from one flower to another. The beautiful colours tend to attract the bees and other insects towards the flowers.

            God created this universe and all creatures; Insan(humans), Hiwanat(animals), Nibatat( 

plants), Jamadat( non-livings). He is Ya-Khaliqu( the Creator); Ya-Awwalu  (The First); Ya-Akharu (The Last); Ya-Baqiu( The Immortal)…All  other creatures are mortal except Him; The Almighty. So, God had designed different programs to keep His creatures, animals or plants, in constant influx by method of reproduction for which He had developed variety of attractions, allurements and needs for the 

creatures to be persistent in the chain process of reproduction. In order, to carry on process of reproductions in flowering plants, The Creator created multicoloured flowers, fragrance, sweat juicy nectar, silky touch petals and charming appearance—so flowers attract insects and bees which carry the task of 

pollen grain transference which is essential for reproduction and giving birth to new generation of plants. That is how! coloured flowers accomplish the Divine Program. Colour of flowers also camouflage the insects thus provide them hiding place also.

Why are the bottoms of cooking utensils blackened?

Why are the bottoms of cooking utensils blackened?

PROF WAQAR HUSSAIN

            There are three main reasons to blacken the bottoms of cooking utensils (not of copper).

First, the black surface absorbs more heat as compared to clean surface. The absorption of heat depends upon the surface. According to Prevost Theory of Heat Exchange: “Every body emits radiation continuously to its surroundings at the rate which depends only on the nature of its surface and temperature and at the same time 

it receives radiation from its surroundings at the rate depending on “the surface” and the temperature of surroundings.” So it is the economical practice to blacken bottoms of utensils to efficiently absorb maximum amount of heat. It not only saves fuel but also reduces cooking time.

              Now the question arises why copper utensils are not turned black. It is due to fact that copper oxidizes in presence of oxygen to form brownish black copper oxide. If it is not polished away copper oxide reacts with CO₂ to form green colour copper carbonate.

Second, bottoms are turned black for aesthetic reason as the fire emits black carbon particles especially yellow flame that blackens the bottom. Imagine for a moment, that the entire utensil has glitter but bottom has ugly black patches! When you yourself started to blacken the bottom, it became a normal, routine practice and soon people accustomed to it. It became normal for the eyes, acceptable for the society and developed as a decorative practice; abnormality turned to normality.

Third, people in some part of Asia are superstitious. There have a concept of “Evil Eye” which they believe to ruin the object on which it gazes. Especially in rural area, this concept is deep rooted. Further, it is more common in women than men. So, for this reason also, the village women started coating black their utensil to ward off evil eye for the safety of their cooked food. For them black colour dispels wicked eye. Even today, many people in Asia, place the handi( a cooking pot made of clay roasted in furnace with black underneath) on the top of roof of their newly constructed building to keep at bay evil eyes. Some time, mothers make a mark black mole on the faces of their beautiful kids to protect their children against evil eye.

Why stars twinkle?

Why stars twinkle?

PROF WAQAR HUSSAIN

            Stars twinkle for two main reasons. The intensity of brightness of stars decreases and increases because of the line-of-sight effect. Moreover, there are disturbance in the gases of the atmosphere around the Earth. Different layers of gases also have different temperature which brings visual changes. The atmosphere is moving around, and there are various currents of different density and temperature, etc. 

           when you look up at star, you are viewing them through 100 miles of atmosphere. The light of stars pass through different density of air, hence it is refracted again and again and when the current of air flow and light of stars have to pass through different sets of air densities, their refraction pattern is changed and consequently the viewer see the light of different intensity and at different places, this appear to viewer as twinkling. 

Why blood moon is red? Is the end of world near?

Why blood moon is red? Is the end of world near?

PROF WAQAR HUSSAIN  

      

  When the shade of earth falls on moon, it is called lunar eclipse. Or one can say when earth comes between sun and moon and moon cannot get sun rays due to presence of earth. Lunar eclipse occurs at full moon. When the light from the sun is completely blocked by the earth in case of full lunar eclipse and only larger wavelengths i.e. orange and red wavelength reaches the surface of moon making it orange or red. While smaller wavelength violet, indigo, blue, green, yellow are blocked by the earth and its atmosphere.

       Many people especially in west fear that the end of world is near. They are getting worried on reading Biblical prediction of Joel 2:31 in common English Bible: “THE SUN WILL BE TURNED TO DARKNESS AND THE MOON TO BLOOD BEFORE THE GREAT AND DREADFUL DAY OF THE LORD COMES”.

        The simple answer for the worried people is; how moon could turn red if the sun is dark. The moon has no light of its own; it just reflects the sun rays. The dark sun simply means, the dark moon and not the red one (It is scientific answer. One can seek religious answer from priests!) 

    Now come to second reason of blood moon; it happens when the sun, earth, moon and mar are in line. This is another false theory as the sequence of planet around the sun disagrees with any role of mar in this phenomenon. From the sun, the planets follow as Mercury, Venus, Earth, Mar….The Mar is out of this optical phenomenon. If one argues that sun rays are reflected from the red coloured planet Mar and these rays fall on the moon, making it red. If, we suppose that such happens, then these rays will fall on the backside of moon that is not visible from the Earth. So, this theory carries no weight.

Why blood moon is red?

Why blood moon is red? 

WAQAR HUSSAIN PROF

       

        When the shade of earth falls on moon, it is called lunar eclipse. Or one can say when earth comes between sun and moon and moon cannot get sun rays due to presence of earth. Lunar eclipse occurs at full moon. When the light from the sun is completely blocked by the earth in case of full lunar eclipse.Consequently, only larger wavelengths i.e.. orange and red wavelength reaches the surface of moon making it orange or red. While smaller wavelength violet, indigo, blue, green, yellow are blocked by the earth and its atmosphere.