Category Science

Giridhar Madras

Giridhar Madras is an Indian professor at the Indian Institute of Science, Bangalore, India.

Education

Madras speaks four languages, English, Hindi, Tamil, and Kannada. Madras received his chemical engineering degree from Indian Institute of Technology at Madras in 1990. He obtained his Ph.D. degree in chemical engineering from Texas A&M University, United States, in 1994. Subsequently, he worked in the University of California at Davis, USA. He returned to India as an Assistant Professor of chemical engineering at the Indian Institute of Science, Bangalore in 1998.

Fields

  • Chemistry

Awards

  • Scopus Young Scientist Award from Elsevier for being the most cited young author in engineering
  • Presidential Swarnajayanthi fellowship by the Department of Science and Technology, India, 2006
  • Shanti Swarup Bhatnagar prize from CSIR, India, 2009
  • J.C. Bose National fellowship, 2014

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Why is it said: An apple a day keeps the doctor away?

          The age-old maxim, ‘An apple a day keeps the doctor away’ was a polite way of saying that this habit would help to prevent constipation and other related ailments. Since it was believed that the juice of a raw apple aided the fermentation of undigested foods.

          Although one might question such a sweeping statement in the highly advanced modern times, none can deny that apples are good for health because of their high nutritious value. Some people have modified this statement and suggested that ‘it keeps the dentist away more than the doctor’. According to the dentists, biting on a crisp apple is an effective way of removing food particles from between the teeth. Eating an apple after meals and cleaning the teeth in the night and morning is the best way to keep the teeth healthy. 

          Apples contain Vitamins A and C. They are rich in cellulose and carbohydrates. They also contain some minerals. This implies that apples also help in the prevention and cure of several deficiency disorders, e.g. scurvy, night blindness etc. as well as in purifying blood. They also aid in healing, protection against cold and building of healthy bones, teeth and gums.

          The presence of these food sources and their utility in keeping the body fit and healthy justifies the old adage.

          Apples are eaten raw, both for taste as well as its beneficial values. An apple contains about five-sixths water and the remaining one-sixth consists of sugar, ascorbic acid (Vitamin C) and other acids, and rough indigestible matter. Apart from their nutritious value, apples are also used for cooking sweet dishes, and cider is brewed from fermented apples.

          Apples belong to the family of Rosaceae. In the ripen state they are usually red, yellow or green. Apples grow in temperate zones, in relatively cold weather. By the end of 300 A.D, a Roman writer named 37 varieties of apple and today hundreds of varieties are available with varying sweetness. 

Kedareswar Banerjee

Kedareswar Banerjee (15 September 1900 – 30 April 1975) was an X-ray crystallographer and director of the Indian Association for the Cultivation of Science, Kolkata. Early in his career he determined the structures of naphthalene and anthracene. In 1931, he worked with Sir William Henry Bragg and developed one of the first direct methods of crystal structure determination. He was Professor of Physics at the Indian Association for the Cultivation of Science from 1943 to 1952 and Director of the Association from 1959 until his retirement in 1965. Between 1952 and 1959 he was Head of the Department of Physics at Allahabad University.

               His interests in crystallography were widespread and, with his death, India has lost a renowned teacher. K. Banerjee joined the research group of Sir C. V. Raman at the Indian Association for the Cultivation of Science (IACS), Calcutta, a premier Indian research institute of India. He worked in various institutions including IACS, the India Meteorological Department, University of Dhaka and Allahabad University and finally retired as the Director of IACS, Calcutta in 1965.

Field

  • X-ray Crystallographic

Institutions

  • University of Allahabad,
  •  India Meteorological Department, University of Dhaka,
  •  Indian Association for the Cultivation of Science

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What is the weight of our atmosphere?

            Our Earth is surrounded by a blanket of air from all sides. This enveloping blanket is called atmosphere. The atmosphere consists of a mixture of more than ten gases. In terms of volume, 78.05% of the atmosphere is nitrogen, 20.94% is oxygen and nearly 1% carbon dioxide. The remaining gases include argon, helium, neon, carbon monoxide, ammonia etc. The atmosphere also contains water vapour and dust particles, hydrocarbon, hydrogen oxide and sulphur compounds in variable amounts.

            Since all these gases are different forms of matter, they exert a downward force on the surface of the Earth and are regulated by the force of gravity. Man is rarely conscious of this weight since it presses on him from all directions, and his body is fully adjusted to it. The weight of the atmosphere can be determined by taking into account the masses of these gases and the force of gravity (weight = mass x gravity). We know that one mole of nitrogen weighs 28 gm. and that of oxygen 32 gm. Mole is the basic unit for measuring the amount of any substance in terms of atoms and molecules. 

Continue reading “What is the weight of our atmosphere?”

What are solar flares?

          A solar flare is defined as a sudden intense brightening of a small part of the sun’s chromosphere near a sunspot group. The brightness of the flare may be five times that of the associated plage or facula. The flare develops in a matter of a few minutes and may last for several hours. In a large solar flare, tremendous energy to the extent of ergs is released.

          Solar flares occur only as a result of sunspot activity. Practically all sunspots produce some flares but certain spots are much more active. Their source of energy is the magnetic fields surrounding the sunspots.

          Such flares are rarely seen in white light because they are an atmospheric phenomenon, with such low density that they’re transparent. On the other hand, their temperature is so high that in the ultraviolet zone, they may equal the intensity of the entire Sun. However, because the flares are most easily observed in Ha (H-alpha) and because the Ha brightening is an extremely accurate indicator, they can be studied well.

          Solar flares emit ultraviolet radiations and X-rays. They also emit great amount of energetic particles and cosmic rays. The particles travel much slower than the light of the flare and reach the vicinity of Earth a day or two later. They pose a potential radiation hazard to human beings in space. During solar flares, jets of particles known as the solar wind, and strong radio frequency electromagnetic radiations are emitted which disrupt radio communications and cause auroras.

          Flares also produce intense streams of electrons. These travel at about one third of the speed of light. 

What are the different types of mirrors?

           Archaeological evidences had established that mirrors made of polished metal were in use during the Iron Age. The Egyptians had silver and bronze mirrors by 2500 B.C.

           A mirror is made of a sheet of glass on the back of which is sprayed a thin layer of silver or aluminium. It produces images by reflection. They obey the laws of reflection. A ray of light strikes the mirror and is reflected into our eyes. The kind and size of the images depend on the shape and structure of the mirror. Do you know how many types of mirrors are there?

          The mirrors can have flat or curved surfaces. A flat mirror is called a plane mirror. The image seen in a plane mirror is called a virtual image. Although we can see it, it cannot be projected onto a screen. This is because the image appears to be formed behind the mirror. The image in a plane mirror is erect but laterally inverted, i.e. the right-hand side of an object becomes the left-hand side in the image and vice versa. The image is always of the same size as the object. The plane mirrors are used in homes for seeing oneself, decorative purposes and in many optical instruments. 

          There are two different types of curved mirrors – convex and concave. The convex mirrors curve outwards and concave mirrors inwards. The image in a convex mirror is always smaller than the object. The image is erect and virtual. The convex mirrors are used as review mirrors in automobiles. They allow the driver to see a large area of the road behind him.

          The image in a concave mirror depends on how far the object is from the mirror. If the object is placed close to the mirror, its image is virtual and magnified. A magnified image is larger than the object. Since they have magnifying properties, the concave mirrors are used as shaving mirrors. If the object is beyond a certain distance from the mirror the nature of image changes. It becomes smaller than the object and upside down. The image now lies in front of the mirror and is said to be real. A real image can be projected onto a screen.

          The curved mirrors also have cylindrical, parabolic and ellipsoidal surfaces. The cylindrical mirrors focus a parallel beam of light to a line focus. A parabolic mirror may be used to focus parallel rays to a real focus. These are used in telescopes and search lights. An ellipsoidal mirror reflects light from one of its two focal points to the other.

          The mirrors are produced by coating the glass surfaces with metallic silver. This is done through a chemical process. Sometimes even copper and gold are used for the purpose. Mirrors are also being produced by vacuum deposition of silver or aluminium on glass surfaces. Most of the mirrors are coated with aluminium because as compared to silver it is less expensive.