Ionized hydrogen atoms and $$\alpha$$-particles with same momenta enters perpendicular to a constant magnetic field, B. The ratio of their radii of their paths $$r_H : r_{\alpha}$$ will be :
Correct option is A. $$2 : 1$$
We know,$$r_H = \dfrac{P}{e\times B}$$
$$r_{\alpha} = \dfrac{P}{2e\times B}$$(As $$\alpha$$ has 2e of charge on it)
$$\dfrac{r_H}{r_{\alpha}} = \dfrac{\dfrac{P}{eB}}{\dfrac{P}{2eB}}$$
$$\implies \dfrac{r_H}{r_{\alpha}} = \dfrac{2}{1}$$
Hence option A is correct answer