Clouds once seen at a particular point may not be there after some time. Why?

When we put a drop of, red ink in 100 ml. of water, we observe that all the water becomes purple in colour after some time. Why ?

The decolourisation of permanganate with oxalate is initially slow, but gains momentum after some time. Why?

A plane electromagentic wave of frequency 25 MHz travels in free space along the x-direction. At a particular point in space and time , E=6.3 hatj V/m . What is B at the point ?

Measure the body temperature between fingers, under the tongue, armpit,folded hands, folded legs etc., Is it the same? Does the body temperature remain the same after jumping ten times?. Why?

A proton and an alpha -particle are simultaneously projected in opposite direction into a region of uniform magnetic field of 2 mT perpendicular to the direction of the field. After some time it is found that the velocity of proton has changed in direction by 90^(@) . Then at this time, the angle between the velocity vectors of proton and alpha - particle is