Why we are drooping in front of the Computer ? Fact file 13

Continuous use of computer without rest can cause lethargy and sleep. The muscles controlling the eye lids may fatigue leading to droopy eyes. The symptoms leading to this is called Computer Vision Syndrome or CVS. The main reasons of  CVS are Pulsed Electromagnetic Radiation (PEMR) and Artificial light from the Monitor and  difficulty in focusing . The Monitor especially the CRT monitor generates PEMR which carries energy radiation. Continuous exposure of eyes to light especially the UV rays from the computer monitor can induce sleep. The retina of eye has photosensitive cells called Rods with Rhodopsin pigment. It undergoes bleaching into Opsin and Retinene when exposed to light. This bleaching reaction elicits nerve impulses which passes into the brain and we see the image by the interpretation of visual signals in the brain.

After the bleaching reaction, resynthesis of Rhodopsin takes place instantly. But if the eye is exposed to light continuously there will not be sufficient time to resynthesize the Rhodopsin. So, as a protective measure, brain induces sleep to close the eyes in order to block light.

Artificial fluorescent light from the monitor is another factor. Artificial fluorescent light is the form of fractioned light which leaves out many segments of the spectral range. Flickering of the screen is also dangerous since the flickering rate is higher than the ‘Flicker-Fusion’ rate of the human eye. CVS is also caused due to bad contrast or excessively or poorly illuminated screen.
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Why Lightning causes Arc blast in wall sockets? Fact File 12


Lightning is the heavy discharge of accumulated charge from clouds into the earth. Its voltage may be as high as 50,000 volts or more. There exists a potential difference between the sky and earth depending on the climatic conditions. In normal sunny days, this potential difference is around 100 volts with negligible current because the air acts as a good insulator. When clouds start to accumulate in the sky, this atmospheric charge increases to 1000 volts or more. If this charge increases further to thousands of volts, sudden discharge of charge takes place which is the lightning strike.The explosion during lightning is the result of Air column breaking.
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