Pari Talks

  Infrared P.K.Ghatak, MD No. 72. Infrared is positioned just outside of the visual range of the humans on the Electromagnetic Spectrum. The wavelength of Infrared is between 700 nanometer to one miter. 57% heat from the sun reaches the Earth by the infrared bands (IR). Without the IR, modern warfare will grind to a halt – thermal signature of projectiles, missiles, machinery and people are precisely located and targeted to shoot them down. From the time men began lightening fire, humans understood heat carried energy from the fire to them in radiation in addition to conduction and convection. Infrared was known long before Ultraviolet was discovered. William Harshel in 1800, discovered Infrared while studying sunlight with a prism. The sun is the primary source of IR for us, in addition other celestial bodies also contribute some. People are generating IR without realizing - every time they switch on a burner, stove or light a candle one generates IR. Usefulness of infrared: Remot...

  Ultraviolet  P.K.Ghatak, MD No 71.  Human eyes are unable to see Ultraviolet (UV), but insects, birds and dogs are capable of seeking objects in UV. Ultraviolet light is longer than X-ray in their wavelength but shorter than the violet light on the Electromagnetic spectrum. Flowers display petals in UV light for bees and other insects to visit, offering nectar and in the process, insects pollinate flowers. A German scientist Johann Ritter was experimenting with light waves beyond the visible parts of the light. He used Silver Chloride painted papers to detect the presence of light waves and in 1801, he detected UV light. The Earth receives UV light mostly from the sun and also from Jupiter, stars, other planets of the solar system, aurora, and white dwarf. Ozone layer in the upper atmosphere blocks UV light, concentration of ozone varies based on location and presence of Ozone destroying substances made by humans.  Hummingbirds have a special retinal receptor for v...