Question

What is the wavelength of light for the least energetic photon emitted in the Lyman series of the hydrogen spectrum, (take $hc \,=\, 1240\, eV\, nm$)

• A. 82 nm
• B. 102 nm
• C. 122 nm
• D. 150 nm

Answer 1

Answer: (C)

Given, $h_{C}=1240 \,eV$
For least energetic photon $E=E_{2}-E_{1}=10.2 \,eV$
We know that, $E=\frac{h c}{\lambda} ; \lambda=\frac{h c}{E} ; \lambda=\frac{1240}{10.2}$
$\lambda=121.56 \approx 122 \,nm$