The longest phase of meiosis is ........

Which one of the following transitions of an electron in a hydrogen atom emits radiation of the lowest wavelength?

The plates of a parallel plate capacitor are charged up to $100\, V$. $A$ $2\, mm$ thick plate is inserted between the plates. To maintain the same potential difference,the distance between the capacitor plates is increased by $1.6\, mm$. The dielectric constant of the plate is:

$A$ film of water is formed between two straight parallel wires of length $10\,cm$ each,separated by $0.5\,cm$. If their separation is increased by $1\,mm$ while still maintaining their parallelism,how much work will have to be done? (Surface tension of water = $7.2 \times 10^{-2}\,N/m$)

Sulphide ores of metals are usually concentrated by froth floatation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

Which of the following pairs of straight lines intersect at right angles?