The ratio of wavelengths for the transition of electrons from the $2^{nd}$ orbit to the $1^{st}$ orbit of Helium $(He^+)$ and Lithium $(Li^{++})$ is (Atomic number of Helium = $2$,Atomic number of Lithium = $3$).

The radius of the third stationary orbit of an electron for a Bohr atom is $R$. The radius of the fourth stationary orbit will be

Energy levels $A, B, C$ of a certain atom correspond to increasing values of energy,i.e.,$E_A < E_B < E_C$. If $\lambda_1, \lambda_2, \lambda_3$ are the wavelengths of radiations corresponding to the transitions $C$ to $B$,$B$ to $A$,and $C$ to $A$ respectively,which of the following statements is correct?

In a hydrogen atom,the electron is moving around the nucleus with a velocity of $2.18 \times 10^{6} \; m/s$ in an orbit of radius $0.528 \; \mathring{A}$. The acceleration of the electron is:

In accordance with Bohr's model,find the quantum number that characterizes the Earth's revolution around the Sun in an orbit of radius $1.5 \times 10^{11} \; m$ with an orbital speed of $3 \times 10^{4} \; m/s$. (Mass of Earth $= 6.0 \times 10^{24} \; kg$)

The radius of the electron's second stationary orbit in Bohr's atom is $R$. The radius of the third orbit will be: