de Broglie's Explanation of Bohr's Second Postulate

Radius of first orbit in $H-atom$ is $a_0$. Then de-Broglie wavelength of electron in the third orbit is

The de-Broglie wavelength associated with electrons revolving round the nucleus in a singly ionised helium atom in first excited state, will be

The De-Broglie wavelength associated with electrons revolving round the nucleus in a hydrogen atom in ground state, will be-

The de-Broglie wavelength of the electron in the first Bohr orbit of the Hydrogen atom is equal to ( $a_B$ denotes the Bohr radius)

De-Broglie wavelength of a body of mass m and kinetic energy E is given by (symbols have their usual meanings):

If an electron in a hydrogen atom, revolving in its second excited state (having radius $4.65 \stackrel{\mathrm{o}}{\mathrm{A}}$ ). what is the de-Broglie wavelength of this electron?

An electron is moving in Bohr's fourth orbit. Its de-Broglie wave length is $\lambda$ . What is the circumference of the fourth orbit?

The ratio of the de-Broglie wavelength of an $\alpha$-particle and a proton of same kinetic energy is