Question

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

• A. 9:4
• B. 9:36
• C. 4:9
• D. 2:3

Hint:

Logic Tip: Wavelength is inversely proportional to energy ($E = hc/\lambda$). A higher atomic number $Z$ means a stronger pull on the electrons, resulting in a much larger energy gap between orbits ($E \propto Z^2$). Since Lithium has a larger $Z$, it emits a much higher energy photon, meaning a much shorter wavelength. Thus, the $He$ to $Li$ wavelength ratio must be $> 1$, eliminating options C and D immediately.

Answer 1

The Correct Option is A