In places of hot climate it is advised that the outer walls of the house should be painted white. Why?

In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Why do Eskimos make double walled houses?

Why there is a shine on the walls after two three days of white washing ?

A convex lens of power 4D is placed at a distance of 40 cm from a wall at what distance from the lens should a candle be placed so that its image is formed on the wall?

Paper delievery boy wants to park his cycle at some point P and deliver the newspaper to house A and B . Where should he park the cycle so that his walking distance AP + Bp will be least ? You can use relfection symmetry here . Let A' be the image of A in the mirror line which is the street here . Then the point P is the ideal place to park the cycle . (where the mirror line and A'b meet ) Can you say why ?

Why is it that during changing weather, one is advised to avoid closed, crowded and air conditioned places like cinema halls, etc.?