General Science GK Questions with Answers – Page 6

Light travels fastest in a vacuum; in any material medium, including carbon disulphide, it slows down, so its speed there (X) is less than its speed in vacuum (Y).

The bulb of a headlight is placed at the principal focus of a concave mirror, so the reflected light leaves as a strong beam of parallel rays that reaches far down the road.

Turmeric is a natural indicator: soap is basic and turns the yellow stain reddish brown, and rinsing with plenty of water removes the soap so the stain turns yellow again.

Thrust is a force and impulse is force multiplied by time, so thrust divided by impulse has the unit 1/second (s⁻¹), which is the unit of frequency.

The cochlea of the inner ear changes the pressure variations of sound into electrical (nerve) signals, which the auditory nerve then carries to the brain.

In glass, light of shorter wavelength travels more slowly, so the glass has a higher refractive index for it and bends it more.

A system whose walls let no heat pass in or out is called adiabatic, so any change in its state happens with zero heat exchange (Q = 0).

Apart from the Sun, Proxima Centauri is the star nearest to the Earth, about 4.24 light years away. Proxima Centauri is a small, dim red dwarf in the constellation Centaurus and cannot be seen with the naked eye.

These are the only two elements that are liquid at standard room temperature and pressure: mercury is a metal and bromine is a non-metal.

Sodium carbonate, called washing soda in its hydrated form Na₂CO₃·10H₂O, removes both temporary and permanent hardness of water. Hard water contains dissolved calcium and magnesium salts, which stop soap from lathering.

H₂S is a colourless gas with the familiar smell of rotten eggs, and the human nose can detect it even in very small amounts.

Nylon 6 is made from a single monomer, caprolactam, whose ring opens on heating and joins up into long polyamide chains.

The Swedish chemist Berzelius proposed around 1813–1814 that each element be written with one or two letters taken from its name, the system still used today.

A soda-acid extinguisher holds a solution of sodium hydrogen carbonate (baking soda) and a small bottle of sulphuric acid; when the two mix, carbon dioxide is released.

Nitrogen gas is the element itself in a very stable form, and plants cannot take it up directly from the soil or the air, so it is not used as a fertilizer.

Lactobacillus turns the lactose sugar of milk into lactic acid, which sours the milk and makes it set into curd.

On heating, sodium bicarbonate releases carbon dioxide gas, whose bubbles make dough rise and turn cakes and bread soft and spongy.

The speed of sound in air increases, not decreases, as temperature rises, so statement B is the incorrect one. Sound in a gas travels faster when the gas is warmer, because its molecules move faster and pass the vibration on more quickly.

The bulb's resistance stays the same, and since power varies as the square of voltage, halving the voltage cuts the power to one-fourth.

Strain is a ratio of two lengths (or two volumes), so its units cancel and it has no dimensions. When a force deforms a body, strain measures the fractional change in its shape or size.