The radius of the thrid Borh orbit for hydrogen is `4.5 A^@`. The radius of fourth Bohr orbit is ____ (fill in the gap)

The radius of Bohr's first orbit in H atom is 0.053 nm. The radius of second orbit in He^+ would be:

The value of bohr's radius for hydrogen atom is:

The radius of innermost orbit of electron in hydrogen atom is 0.53A^@ . What are the radii of orbits of electron in first and second excited states?