If the potential difference used to accelerate electrons is increased four times, by what factor does the de-Broglie wavelength associated with the electrons change?

When the string is stretched between two rigid supports, under certain tension and vibrated

Simple microscope is used to see the object first in blue light and then a red light. Due to the change from blue to red light, its magnifying power

The inductive reactance of a coil is ' $R$ ' $\Omega$. If inductance of a coil is tripled and frequency of a.c supply is also tripled, then new inductive reactance will be