How is the Rainbow formed?

During the rainy season you might have observed a bow shaped multicoloured strip in the sky. This is called rainbow. This strip has seven colours-red at the top and violet at the bottom. Other colours lie in between these two. How is the rainbow formed?
The sunlight which appears to be white is actually composed of seven colours. These seven colours are-Violet, indigo, blue, green, yellow, orange and red. The wavelength-wise distribution of these colours is called spectrum. After the rains, the atmosphere is full of small water-drops. When the white light coming from the sun enters these drops, its seven colours are separated. These rain-drops work like prisms. As the prism separates the seven colours of white light, these drops also sweparate the different colours. The separation of seven colours of the sunlight is called dispersion. These colours after being totally reflected from the back side of the rain drops come out as separate colours. When the rays of these colours reach our eyes, they give us the appearance of the rainbow. The rainbow is circular because the sun is also circular. Sometimes a second rainbow can also be seen. This is called secondary rainbow. This is fainter in comparison to the first one and the sequence of its colours is reversed i.e. violet colour occupies the upper most position while the red is the lower most. This rainbow is formed due to those rays which have been reflected twice inside the water drops. The rainbow is generally seen only when the sun is at our back and the cluster of water drops are in front of our eyes, i.e. when we stand in between the sun and the cluster of water drops. It is essential for the formation of the rainbow that the sun is shining after the rain. It is also essential that the sun, our eyes and the centre of the rainbow lie on the same straight line. To remember the order of colours in the spectrum, we should remember the word VIBGYOR. Each letter of this word represents one colour i.e. V for violet, I for indigo, B for blue, G for green, Y for yellow, O for orange and R for red.

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Why does the dog go mad?

 Dog is regarded as a faithful friend of man. But when it goes mad it is most dangerous. Biting by a mad dog leads to death if not treated properly. When a dog suffers from a disease called 'rabies', it goes mad. This disease is caused by a virus which is carried by the air or some wild animals and enters the dog's body through some cut or wound in its skin.
The virus is bullet shaped having a diameter of about 70 millimicron and a length of about 210 millimicron. It moves from the saliva-infected wound through sensory nerves to the central nervous system, multiply there and destroy brain cells. These viruses start showing their effect in 4 to 6 weeks' time. During this period the dog becomes lazy, suffers from fever and has no interest in food. When these viruses affect the brain, the dog gets excited. It growls and barks. saliva froths from the mouth. During this period, the dog can bite anybody. This is the stage when the dog is said to be mad. After such symptoms appear in the dog, it is likely to die within 3 to 5 days. When a mad dog bites a man, the viruses present in its saliva enter the man's body through the wound caused by the biting. Initially the victim experiences mental weakness and uneasiness followed by fever. Anxieties invade him. He suffers from lack of sleep and feels frightened. The muscles in the throat get slackened and he faces difficulties in swallowing food or drinking any liquid. He is afraid of water. That is why this disease is also called 'hydrophobia' which means 'fear of water'. The signs of this disease appear in the victim in one to three months from the time of dog-bite. If the dog has bitten at an upper part like the neck, mouth or head, it may take less time for the symptoms to develop. In cases of dog-bites, the affected portions should be immediately cleaned and arrangements made to start giving anti-rabies injections to the victim within three days of the bite. The dog should be watched for the next five days. If the dog does not die in that period, it should not be treated as a mad dog, and the treatment should be stopped since a mad dog must die within five days. A few years before, a daily injection of vaccine was given for 14 days or longer depending on the severity of rabies infection. In the early 1970s a new vaccine was tested. Now a days 7 to 10 injections are given, in case of a mad dog bite, to persons depending on the location of bite and number of bites on the body. The virus of rabies also attacks foxes, jackals, cats and rats. But they rarely transmit these viruses to human beings, because they have least contact with us.

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How do animals and plants survive in deserts?

A desert is an area where there is very little water and there is sand all around. Due to the scarcity of water, it is very difficult for animals as well as plants and trees to survive. Only those plants and animals which need very small quantities of water can survive in deserts.
There is a great variation in the temperatures of the days and the nights of deserts. Days are very hot, while nights are cool. To protect themselves from heat, during the day, the desert animals hide themselves in bushes. Whenever there is some rain, plants and animals store water inside their bodies. In deserts, you find many kinds of animals. Snails are found in abundance. American deserts have a kind of rat called 'pack rat'. A kind of animal named 'Jerboa' is found in the deserts of north Africa and Asia. Its hind legs are longer and it resembles the kangaroo. A variety of the wolf is also found in the Arab and African deserts. many kinds of lizards, owls, insects and ants are seen in derserts. All of these need very little quantity of water for survival because loss of water in the form of sweat and urine is very small. They excrete small quantities of urine which is very rich in urea nad uric acid. The camel occupies a very high position among the animals found in the deserts. It is also called the ship of the deserts. It survives on a diet of dry grass and thorny plants. There is a lot of fat accumulated in its hump and it is source of energy to the camel. It can survive without drinking water for several days. Water evaporates from its body at a slow rate. It can drink 25 gallons of water at one time. Its nose, ears and eyes are so constructed that they are not affected by sands. Mainly, two kinds of plants are found in deserts. One is shrub and the other is cactus. The shrubs have more of thorns and less of leaves. Because of lesser number of leaves, evaporation of water present in these plants is very slow. The trunk of cactus is thick and flashy. It has no leaves. It has only thorns. The upper layer of the trunk is very hard and hence water remains stored in the trunk. In some cacti, the ends of the thorns are pointed towards the earth. The dew drops deposited on these ends fall on the earth and thus moisture is maintained below the cacti. Their roots are also spread far and wide inside the earth. After long dry periods even if there is a little rain these roots immediately absorb water. The root of some cacti do not allow other plants to grow near them and thus the possibilities of more food and water increases.

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What is hypnotism?

Hypnotism is an art, with the help of which the mental state of a human being is so changed that he starts working according to the directions of the hypnotist. Man has been using hypnotic power since ancient times.
Previously, this was used to demonstrate some mysterious power, magic or miracles. Today, however, hypnotism is being studied in a scientific manner. This was started by Franz A. Mesmer, a doctor from Vienna. Hypnotism was known as 'mesmerism' for a long time after the name of Mesmer. The word 'hypnotism' was used for the first time in 1840 by James Braid, a surgeon from Scotland. This word has originated from the Greek word 'hypnos' meaning 'state of sleep'. In fact, a hypnotised person appears to be drowsing. His brain is so much influenced that he does any work according to the directions of the hypnotist. Hypnotic power is used over those persons only who are fully willing and ready to co-operate. Nobody can be hypnotised against his wishes. The person to be hypnotised is asked to sit in a dark room. The hypnotist then repeatedly tells his subject in a very calm voice to relax and sit comfortably. Thereafter, the subject is asked to concentrate his attention and focus his eyes on some object. When he gazes at that object for a long time, his eyes start getting tired. When this happens, he is asked to close his eyes. Now the subject is in a state of sleep. The hypnotist, at that moment starts giving his suggestions and directions to him. He is now hypnotised and does all that the hypnotist asks him to do. Hypnotism can make a person feel as if he is blind, deaf or dumb. It can make him shiver. Hypnotism can be used to frighten people. So much so that under the influence of hypnotism, a man can do things which he will never do in his normal state. When he regains his normal state, he forgets all that he did in hypnotised state. Hypnotism is being used very much these days in the treatment of patients suffering from various diseases. Dr. S. Del of England used to extract the teeth of his patients without putting them under anasthesia. Using this, he even operated upon the lungs of many people Hypnotism can also be used in removing mental anxieties.

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