Physics

The boiling point is the temperature at which the vapour pressure of the liquid equals the environmental pressure surrounding the liquid. Atmospheric pressure is due to air above any given point. The atmospheric pressure at high altitudes like hill station is less than at the sea level.Thus, vapour pressure will equal atmospheric pressure at a comparatively low temperature. Thus, the boiling point of water is reduced less than at sea level.

450 mm Hg denotes the air pressure.

Optical filters are devices that selectively transmit light in a particular range of wavelengths, that is, colors, while blocking the remainder. They are commonly used in photography (where some special effect filters are occasionally used as well as absorptive filters), fluorescence microscopy, spectroscopy, clinical chemistry, colour stage lighting, etc.

Before transferring the fish, the position is the man with the fish and the bucket of water. After transferring the position is: the man without the fish, but the fish inside the water in the bucket. Thus to know whether there is any change in weight, it is enough to consider whether there is any change in weight when the fish in air is transferred into the water. The answer is there is no change as when in water though it loses weight due to upthrust of water on it, the level of water increases and exerts an equal force at the bottom.So, (c) is correct.