The SI unit of intensity of illumination (illuminance) is the lux. An illuminance of 1.0 lux is produced by 1.0 lumen of light shining on an area of 1.0 m^2.

When two different waves having different velocities are overlap with each other and produce a new one it is called Interference. In the case of rain water it happens.

Electron will move towards the high potential i.e. B point because if there is any potential difference the elecric line of forces terminate from higher to lower potential.

Materials used to make raincoats have high surface tension because due to surface tension water droplets do not stick to the material.