Physics - Study Mode
[#1311] Why does the sea appear blue in colour?
Correct Answer
(C) Scattering of the sunlight by water molecules
Explanation
Solution: When sunlight hits the surface of sea or ocean, some of the light gets reflected back, whereas, most of the longer wavelengths such as red, orange and yellow penetrate sea water and get absorbed by the water molecules. So only the shorter wavelengths of light which contain violet and blue colors are reflected back to reach our eyes. Hence the sea water appears blue.
[#1312] The sky appears blue because
Correct Answer
(C) The atmosphere scatters blue colour more than the others
Explanation
Solution: Gases and particles in Earth's atmosphere scatter sunlight in all directions. Blue light is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.
[#1313] During washing of clothes, we use indigo due to its
Correct Answer
(B) Proper pigmental composition
Explanation
Solution: Indigo is a dye different than any other. It does not require any mordant. Rather it is dyed through a living fermentation process. The process “reduces” the Indigo, changing it from blue to yellow. In this state, it dissolves in an alkaline solution. The fibre is worked in the solution, or “vat”. When brought out to the air, it is a bright green. Slowly the air changes it to the beautiful deep and rich blue of Indigo.
[#1314] When heated from 0 to 100 o C volume of a given mass of water will :
Correct Answer
(D) Decrease and then will increase
Explanation
Solution: From water at 0°C to water at 4°C, on addition of heat, the water surprisingly, contracts till it reaches maximum density at 4°C. This negative thermal expansion is termed as the anomalous expansion of water.
From water at 4°C to water at 100°C, water shows a positive cubical thermal expansion like other substances and gradually expand with the increase in temperature.
[#1315] When a bottle of perfume is opened in one corner of a room the smell spreads soon throughout the room. This is an example of
Correct Answer
(D) Diffusion
Explanation
Solution: When a bottle of perfume is opened in a corner of a room, the scent soon spreads all over the room. This physical procedure is called diffusion, due to which the liquid or gaseous molecules travels from the area of higher density to that of the lower density of that substance.