The pair of gases responsible for acid rain are

Two identical piano wires have a fundamental frequency of $600 \text{ Hz}$ when kept under the same tension. What fractional increase in the tension of one wire will lead to the occurrence of $6 \text{ beats per second}$ when both wires vibrate simultaneously?

The alum used for purifying water is

Below are two statements. One is labeled as Assertion $(A)$ and the other as Reason $(R).$
Assertion $(A):$ Gypsum is used to make boards for fireproof walls.
Reason $(R):$ Gypsum is unstable at high temperatures.
In the context of the above statements,choose the correct answer from the options given below:

The magnetic needle of a tangent galvanometer is deflected at an angle $30^{\circ}$ due to a magnet. The horizontal component of the Earth's magnetic field is $0.34 \times 10^{-4} \text{ T}$,which is along the plane of the coil. The magnetic field due to the magnet is:

In which of the following reactions is the product an ether?