Time left 1 Lux is the SI unit of intensity of illumination luminous efficiency luminous flux luminous intensity 2 On a rainy day, small oil films on water show brilliant colours. This is due to dispersion interference diffraction polarization 3 Point A is at a lower electrical potential than point B. An electron between them on the line joining them will move towards A move towards B move at right angles to the line joining A and B remain at rest 4 Materials for rain-proof coats and tents owe their water-proof properties to surface tension viscosity specific gravity elasticity 5 RADAR is used for locating submerged submarines receiving a signals in a radio receiver locating geostationary satellites detecting and locating the position of objects such as aeroplanes 6 Sound of frequency below 20 Hz is called audio sounds infrasonic ultrasonic supersonics 7 On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because mercury is a metal density of mercury is greater than that of water cohesion of mercury is greater than its adhesion with glass cohesion of water is greater than its adhesion with glass 8 Suitable impurities are added to a semiconductor depending on its use. This is done in order to increase its life enable it to withstand higher voltages increase its electrical conductivity increase its electrical resistivity
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