Question

Some of the wave lengths observed in the emission spectrum of neutral hydrogen gas are $912,1026,1216,3646,6563$ $\mathring{A}$. If broad band light is passing through neutral hydrogen gas at room temperature , then the wavelength that will not be absorbed strongly is

• A. $1026\mathring{A}$
• B. $1216\mathring{A}$
• C. $912\mathring{A}$
• D. $3646\mathring{A}$

Answer 1

Answer: (D)

Energy of a photon with wavelength $\lambda$ is
$E=\frac{12400\left(eV.\mathring{A}\right)}{\lambda \left(\mathring{A}\right)}$
Energies of wavelengths (of photons) observed in emission spectrum are
$E_1=\frac{12400}{912}=13.5eV$
$E_2=\frac{12400}{1026}=12.08eV$
$E_3=\frac{12400}{1216}=10.2eV$
$E_4=\frac{12400}{3646}=3.4eV$
When these radiations pass through neutral hydrogen gas at room temperature, as all of atoms are probably in their ground states, absorbed energy must be more than or equal to $10.2eV$.

So, $\lambda =3646\mathring{A}$ wavelength is not strongly absorbed by the given sample.