Power at the distance $r$ from source, $P=\frac{P_0}{4 \pi r^2}$
Each photon emits one electrons.
Also, $P \propto N$
$N$ is the number of photons
$N \propto \frac{1}{r^2}$ $\Rightarrow \frac{N_2}{N_1}=\frac{r_1^2}{r_2^2}$
$\frac{N_2}{N_1}=\frac{0.5^2}{1^2}=\frac{1}{4}$
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| List-$I$ | List-$II$ |
| $E$ is independent of $d$ | A point charge $Q$ at the origin |
| $E \propto \frac{1}{d}$ | A small dipole with point charges $Q$ at $(0,0, l)$ and $- Q$ at $(0,0,-l)$. Take $2 l \ll d$. |
| $E \propto \frac{1}{d^2}$ | An infinite line charge coincident with the x-axis, with uniform linear charge density $\lambda$ |
| $E \propto \frac{1}{d^3}$ | Two infinite wires carrying uniform linear charge density parallel to the $x$-axis. The one along ( $y=0$, $z =l$ ) has a charge density $+\lambda$ and the one along $( y =0, z =-l)$ has a charge density $-\lambda$. Take $2 l \ll d$ |
| plane with uniform surface charge density |
