The wavelength of the radiation emitted is $\lambda_0$ when an electron jumps from the second excited state to the first excited state of hydrogen atom. If the electron jumps from the third excited state to the second orbit of the hydrogen atom, the wavelength of the radiation emitted will be $(20\lambda_0/x)$. The value of $x$ is

For hydrogen atom, $\lambda_1$ and $\lambda_2$ are the wavelengths corresponding to the transitions $1$ and $2$ respectively as shown in figure. The ratio of $\lambda_1$ and $\lambda_2$ is $x/32$. The value of $x$ is

A pure silicon crystal at temperature $300$ K has electron and hole concentration ($n_i$) $10^{16}$ per m$^3$ each and $10^{21}$ phosphorus atoms ($n_e$) are added per cubic metre. The new hole concentration in silicon crystal is

If transistor having $\alpha = 0.9$, is used in CE configuration, then for a change of $0.4$ mA in base current, what will be the change in collector current?