In the Rutherford's alpha scattering experiment, as the impact parameter increases, the scattering angle of the alpha particle

Three energy levels of hydrogen atom and the corresponding wavelength of the emitted radiation due to different electron transition are as shown. Then,

A radioactive sample has half-life of 3 years. The time required for the activity of the sample to reduce to $$\frac{1}{5}$$th of its initial value is about

In the following equation representing $$\beta^{-}$$ decay, the number of neutrons in the nucleus $$X$$ is

$${ }_{83}^{210} \mathrm{Bi} \longrightarrow X+e^{-1}+\bar{v}$$