Why does a soft plastic bag weight the same when empty as when filled with air at atmosphere pressure?

Why does a ray of light bend when it travels from one medium into another?

Why does a piece of red glass when heated and taken out glow with green light?

Why does an object float or sink when placed on the surface of water?

Why does the temperature of a gas rise when it is suddenly compressed?

Why NO become brown when exposed in air?

Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why?

A manometer reads the pressure of a gas in an enclosure as shown in Fig. 10.25 (a) When a pump removes some of the gas, the manometer reads as in Fig. 10.25 (b) The liquid used in the manometers is mercury and the atmospheric pressure is 76 cm of mercury. (a) Give the absolute and gauge pressure of the gas in the enclosure for cases with mercury)

A sphere ,a cubeand a thin circular plate,all made of the same meteriel and having the same mass are initially heated to a temperature of 200°C .Which of them will cool fastest and which one slowest when left in air at room temperature?

Why does a gun recoil when a bullet is fixed.

Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?