On the basis of Bohr's model,the radius of $3^{rd}$ orbit is

Which of the following is correct regarding Bohr's theory?

The work function of sodium metal is $4.41 \times 10^{-19} \ J$. If photons of wavelength $300 \ nm$ are incident on the metal,the kinetic energy of the ejected electrons will be $\left( \dots \right) \times 10^{-21} \ J$. (Given: $h = 6.63 \times 10^{-34} \ J \cdot s; c = 3 \times 10^{8} \ m/s$)

Calculate the energy associated with the first orbit of $He^{+}$. What is the radius of this orbit?

Which of the following represents the wavelength of a spectral line of the Balmer series of the $He^{+}$ ion? ($R=$ Rydberg constant,$n > 2$)

The energy of an electron in the second Bohr orbit of a hydrogen atom is: