COMEDK 2025 Morning Solved Paper

Concept:The Balmer series corresponds to hydrogen transitions to the $n=2$ energy level, and its lines lie in the visible region of the electromagnetic spectrum.Explanation:The wavelength of any Balmer line is given by: $$\frac{1}{\lambda} = R_H \left( \frac{1}{2^2} - \frac{1}{n^2} \right)$$ where $n = 3, 4, 5, \dots$ and $R_H \approx 1.097 \times 10^7 \, \text{m}^{-1}$ is the Rydberg constant.The first few calculated wavelengths are:• $n=3 \to 2$ (H$\alpha$): $656.3 \, \text{nm}$• $n=4 \to 2$ (H$\beta$): $486.1 \, \text{nm}$• $n=5 \to 2$ (H$\gamma$): $434.0 \, \text{nm}$• $n=6 \to 2$ (H$\delta$): $410.2 \, \text{nm}$• The series limit (as $n \to \infty$) is $364.6 \, \text{nm}$.The visible spectrum ranges from about $380$ to $750 \, \text{nm}$. All principal Balmer lines fall between $364.6 \, \text{nm}$ and $656.3 \, \text{nm}$, which is largely within the visible range.Therefore, the entire Balmer series is observed in the visible region.Answer:Option a – The series is in the visible region.