Random facts-I
Random facts-I
why do we get headache?
Veins and arteries on the surface of the brain are sensitive to pain. We feel the headache when pain signals are sent to the brain by nerves in the face, neck and the back.The reason of a common headache are many and varied .We get a headache when the muscles in our eyes get strained.A headache can also occur when the tiny bones in the inner ear which pick out sound for us to hear get tired or if our neck muscles get strained.Emotional upset,aching teeth ,sores in mouth or constipation can also include a headache.There is one form of headache called migraine which periodically occurs in some persons for no apparent reasons.
How does a lie detector work?
A lie detector works on the principle that s person who tells a lie is nervous and under stress .Under such conditions his or her body undergoes some physiological changes.These changes include increase in the heart beat rate,blood pressure and perspiration on palms and soles .These changes are monitored by a lie detector .The person to be examined is made to wear a chest band,
a blood pressure cuff and electrodes on his palms. He is then subjected to a series of questions in order to see his or her reactions.
How is a photograph produced in earlier times?
when we open and close the shutter of a camera quickly , light comes in and strikes the film .When this happens, a chemical reaction takes place on the light sensitive film. Certain tiny grains of silver bromide undergo a change .The film is taken out of the camera and treated with various chemicals to make the print visible and prevent further changes when exposed to light .Digital camera are a recent development.They convert the image they receive into electrical signals that are stored .These signals can then be read by a computer are used to produce a picture on the screen which can be printed out.
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