When the electron orbiting in hydrogen atom goes from one orbit to another orbit (principal quantum number $=n$ ), the de-Broglie wavelength ( $\lambda$ ) associated with it is related to $n$ as

A constant force acts on two different masses independently and produces accelerations $\mathrm{A}_1$ and $A_2$. When the same force acts on their combined mass, the acceleration produced is

When cell of e.m.f. ' $E_1$ ' is connected to potentiometer wire, the balancing length is ' $l_l$ '. Another cell of e.m.f. ' $E_2$ ' $\left(E_1>E_2\right)$ is connected so that two cells oppose each other, the balancing length is ' $l_1$ '. The ratio $E_1: E_2$ is

A graph of magnetic flux $(\phi)$ versus current $(I)$ is shown for four inductors $\mathrm{P}, \mathrm{Q}, \mathrm{R}, \mathrm{S}$. The largest value of self-inductance is for inductor