Explain why the surface of a lake freezes first.

Way do marine animals live deep inside o lake when the surface of the lake freezes?

Explain why the surface of mortar and pestle (silbatta) used for grinding is etched again after prolonged use?

A point source of light is placed directly below the surface of a lake at a distance h from the surface. Find the area surface of a lake at a distance h from the surface. Find the area on water from which the light will come out from water. [(pih^(2))/((mu^(2)-1))]

Explain why the use of goggles enables an underwater swimmer to see clearly under the surface of a lake.

In cold countries , in wingter, even when the water of lakes freezes, aquatic animals and plants can survive. How do you think it is possible? Explain in detail.

Statement-1: Upthurst on a solid block of iron when immersed in a lake will be less on the surface than on the bed of the lake. Statement-2: On the surface of the lake density of water will be less than that at the bed and upthrust depends on the density of liquid.

In cold countries, in winter, even when the water of lakes freezes, aquatic animals and plants can survive. Give reason