Question

The transition from the state n=4 to n=3 in a ${He}^{+}$ ion results in ultraviolet radiation. Infrared radiation will be obtained in te transition from:

• A. $n=2\to n=1$
• B. $n=3\to n=2$
• C. $n=4\to n=2$
• D. $n=5\to n=4$

Answer 1

The correct option is D $n=5\to n=4$

Assuming, that n =4 to n=3 gives the ultraviolet radiation for certain hydrogen like atom, we use the following formula,

IR corresponds to the least value of $(\frac{1}{n_1^2}$ - $\frac{1}{n_2^2})$ i.e from Paschen, Bracket and Pfund series. Thus the transition corresponds to $n=5\to n=4$