Insights Static Quiz -30, 2018

Solution: d)

It is a modified previous year UPSC question.

First statement is right as it is its particle nature of light that scatters it. (https://sciencing.com/diffused-light-5470956.html)

Second statement is correct. Light is diffused after being scattered by particles in atmosphere (or in any medium)

Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue color of the sky and the yellow tone of the sun itself. This involves gas molecules.

Solution: d)

It is a modified previous year UPSC question.

Most of us will have used a product containing sodium sulfate, though oddly it is present in a role that has no practical function. Powdered detergents for washing clothes usually contain sodium sulfate simply to bulk up the product, making detergent manufacturers the biggest users of the compound. It does nothing for the wash, but as a very cheap, pH neutral substance that readily dissolves in warm water, it simply passes through the system, making the product less costly to produce per unit weight. There isn’t as much of it around as there used to be, though, as powder has declined in popularity and there is no need for filler in liquids and gels. Our compound is sometimes confused with sodium lauryl sulfate (also known as sodium dodecyl sulfate) and sodium laureth sulfate which are surfactants used in a range of cleaning products from detergents to toothpastes, but both these compounds are quite complex organic structures which aren’t produced from basic sodium sulfate.

Our sulfate also turns up as a fining agent – not in the more familiar environment of wine or beer fining, but in making glass. In the alcoholic drinks, the fining agent’s role is to extract organic substances that make the liquid cloudy, where in glass it picks up scum and prevents small bubbles from forming. But perhaps the most interesting application of sodium sulfate is in the rapidly advancing world of solar energy heat storage.

As solar thermal power plants, which concentrate incoming light with mirrors to store energy in the form of heat, become more common, there is a need to hold onto that heat before using it. Sodium sulfate takes a high amount of energy to change from solid to liquid and goes through a second phase change at around 32 degrees Celsius when it changes to the anhydrous form, which means that it can store considerably more heat energy than would be expected for any particular mass. Although it isn’t appropriate for the high temperature systems that store heat directly from solar collectors, it has the potential to be valuable in secondary solar facilities, for instance where the heated material gradually releases the heat to warm a building.

Second statement is wrong as it’s Sodium silicate that is used to keep washing powder dry. (https://www.marketizer.com/articles/uses-and-applications-of-liquid-and-solid-sodium-silicate-2735414.htm)

Solution: d)

A transverse wave is a moving wave that consists of oscillations occurring perpendicular (right angled) to the direction of energy transfer (or the propagation of the wave).

If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y–z plane.

Light is an example of a transverse wave, while sound is a longitudinal wave. A ripple in a pond and a wave on a string are easily visualized as transverse waves.

Longitudinal waves are waves in which the displacement of the medium is in the same direction as, or the opposite direction to, the direction of propagation of the wave. Mechanical longitudinal waves are also called compressional or compression waves, because they produce compression and rarefaction when traveling through a medium, and pressure waves, because they produce increases and decreases in pressure.

Solution: b)

It is also based on previous UPSC question.

Option A is wrong as it is oxides of nitrogen

Option B is wrong, as photochemical smog requires sunlight and occurs in the morning or in afternoon

Option C is right ( see explanation below – second paragraph)

Photochemical smog forms from a complex process, however the source of it is quite apparent. The largest contributor is automobiles, while coal-fired power plants and some other power plants also produce the necessary pollutants to facilitate its production. Due to its abundance in areas of warmer temperatures, photochemical smog is most common in the summer.^[3]

It forms in the morning when a tremendous number people are driving their vehicles to work. Nitrogen oxides produced in the car engine are introduced into the atmosphere, which may combine with water to form nitric acid or react with sunlight to produce singular oxygen atoms, which then combine with molecular oxygen to produce ozone.^[2] The nitric acid may precipitate to the Earth resulting in acid rain, or remain in the smog. Due to the direct production of it by vehicles, the smog forms over cities where many people may encounter its adverse health effects.

Hotter days mean more photochemical smog, especially in the densely populated cities such as those mentioned above. As more and more urban populations arise around the globe, this problem is only expected to increase

http://energyeducation.ca/encyclopedia/Photochemical_smog

Solution: d)

Based on previous year UPSC question on sound waves

Air is a gas, and a very important property of any gas is the speed of sound through the gas. Why are we interested in the speed of sound? The speed of “sound” is actually the speed of transmission of a small disturbance through a medium. Sound itself is a sensation created in the human brain in response to sensory inputs from the inner ear. (We won’t comment on the old “tree falling in a forest” discussion!)

Disturbances are transmitted through a gas as a result of collisions between the randomly moving molecules in the gas. The transmission of a small disturbance through a gas is an isentropic process. The conditions in the gas are the same before and after the disturbance passes through. Because the speed of transmission depends on molecular collisions, the speed of sound depends on the state of the gas. The speed of sound is a constant within a given gas and the value of the constant depends on the type of gas (air, pure oxygen, carbon dioxide, etc.) and the temperature of the gas.

The speed of sound in the atmosphere is a constant that depends on the altitude, but an aircraft can move through the air at any desired speed. The ratio of the aircraft’s speed to the speed of sound affects the forces on the aircraft. Aeronautical engineers call the ratio of the aircraft’s speed to the speed of sound the Mach number, M. If the aircraft moves much slower than the speed of sound, conditions are said to be subsonic, 0 < M << 1, and compressibility effects are small and can be neglected. If the aircraft moves near the speed of sound, conditions are said to be transonic, M ~ 1, and compressibility effects like flow choking become very important. For aircraft speeds greater than the speed of sound, conditions are said to be supersonic, 1 < M < 3, and compressibility effects are important. Depending on the specific shape and speed of the aircraft, shock waves may be produced in the supersonic flow of a gas. For high supersonic speeds, 3 < M < 5, aerodynamic heating becomes very important. If the aircraft moves more than five times the speed of sound, conditions are said to behypersonic, M > 5, and the high energy involved under these conditions has significant effects on the air itself. The Space Shuttle re-enters the atmosphere at high hypersonic speeds, M ~ 25. Under these conditions, the heated air becomes an ionized plasma of gas and the spacecraft must be insulated from the high temperatures.

https://www.grc.nasa.gov/www/k-12/airplane/sound.html