Question

What is the maximum wavelength of line of Balmer series of hydrogen spectrum? (R = 1.09 ??10 m)

• A. 400 nm
• B. 660 nm
• C. 486 nm
• D. 434 nm

Answer 1

Answer: (B)

660 nm

Answer 2

For maximum wavelength in the Balmer series, n = 3 and n = 2. $\therefore\quad \frac{1}{\lambda}=1.09\times10^{7}\times1^{2}\left(\frac{1}{2^{2}}-\frac{1}{3^{2}}\right)$ $\Rightarrow\quad \frac{1}{\lambda}=1.09\times10^{7}\times1\left(\frac{1}{4}-\frac{1}{9}\right)$ $\quad\quad\quad\ =1.09\times10^{7}\times1\left(\frac{5}{36}\right)$ $\Rightarrow\quad \lambda=1.09\times10^{7}\times1\left(\frac{5}{36}\right)$ $\quad \quad \quad = 6.60 ??10^{-7} m = 660$ nm