Both infrared and microwave bands are invisible to the human eye . Then how are IR and microwave images from remote sensing satellites printed ? How do they substitute the wavelengths ?
Why does sunlight falling on the ground through small holes of any shape appear circular ?
turns a purplish-blue colour . The discoloration of the skin could also represent a high level of an abnormal form of haemoglobin in the blood circulating throughout your body . Haemoglobin is the protein responsible for transfer oxygen in your blood .
Cold temperatures can also cause your fingernails to turn blue . That ’ s because cold temperatures force your blood vessels to constrict . The narrow pathways make it difficult for the right amount of oxygen-rich blood to get to your nails . If normal nail colour returns upon warming up or massaging your hands , the blue colour was likely due to the that part of your body not getting enough blood supply because of cold temperatures .
Both infrared and microwave bands are invisible to the human eye . Then how are IR and microwave images from remote sensing satellites printed ? How do they substitute the wavelengths ?
SCIENCE FACTS
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bands and hence can be used as photographic plates for detecting and measuring some of these radiations .
Satellites nowadays use sensors whose working principle is based on photoelectric effect , converting radiation reaching the sensor into electric charge , which can then be easily measured and processed . Essentially , the energy detected over a given spectral band , whether it is in the visible , infrared or microwave band , is converted to an array of digits corresponding to the energy range and radioed to ground stations . After receiving it , those digital values corresponding to the measured energy range ( known as grey levels ) are finally printed on a computer screen as a picture or as a conventional photograph .
Why does sunlight falling on the ground through small holes of any shape appear circular ?
Both infrared and microwaves are part of the electromagnetic spectrum , which stretches from radio waves to gamma rays . Each band of this spectrum corresponds to a small range of frequencies . Each frequency is uniquely connected with an energy level . The total spectrum is very wide . Our eyes respond only to a very small band called the visible band . However , different chemicals do react to certain higher or lower level of energy
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hen light rays travel a long distance they do so in parallel lines . Since the entire density of rays pass through the miniature holes , the shape of the ( sun ) light corresponds to the shape of the prototype object from where the light emanates . Since the shape of the sun is circular the shape of the sunlight is also circular . Such phenomena are quite common during eclipses . It will be interesting to note that the changes in the shape of the ( sun ) light falling on the walls or on the ground correspond to the shape of sun / moon , as the eclipse progresses . When the light rays pass through the trees or very small holes ( in thatched roofs ) the images are circular .
WINSPIRE : Empowering youth | February , 2017