The ratio of the radii of the orbits of the electron in the ground state of hydrogen and He+ is
Correct: A
The radius of the orbit of the electron in the ground state of hydrogen is given by the equation r = a0, where a0 is the Bohr radius. For He+, the radius is given by r = a0/Z, where Z is the atomic number. Since Z = 2 for He+, the radius is r = a0/2. So, the ratio of the radii is a0 : a0/2 = 2:1