The time taken by a photoelectron to come out after the photon strikes is approximately

Which of the following ethers is a liquid at room temperature?

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?

Two wires of the same material and length but diameters in the ratio $1:2$ are stretched by the same force. The elastic potential energy per unit volume for the wires, when stretched by the same force, will be in the ratio: (in $:1$)

During the titration of $0.1 \, M$ $CH_3COOH$ and $0.1 \, M$ $KOH$ solution,what will be the $pH$ of the solution after $40\%$ neutralization of the acid? [$K_a$ for $CH_3COOH = 2 \times 10^{-5}$]

$Na^+$,$Mg^{2+}$,$Al^{3+}$,and $Si^{4+}$ are isoelectronic. What is the order of their ionic radii?