Question

When electron of $1.0gm$ atom of hydrogen undergoes transition giving the spectral line of lowest energy in visible region of its atomic spectra, the wavelength of radiation is:

• A. $6564A$
• B. $3640A$
• C. $5000A$
• D. $4312A$`

Answer 1

The correct option is A $6564A$

$\frac{1}{\lambda }=1.097\times {10}^7\{\frac{1}{2^2}-\frac{1}{3^2}\}$
$=1.097\times {10}^7\{\frac{1}{4}-\frac{1}{9}\}$
$=1.097\times {10}^7\times \frac{5}{36}$
$\lambda =\frac{36}{5\times 1.097\times {10}^7}\Rightarrow$
$\lambda =656.33nm$
$\lambda =6564A$

Hence the answer is $6564A$