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If λ1 and λ2 are the wavelengths of the first members of the Lyman and Paschen series respectively, then λ1 : λ2 is(a) 1 : 3(b) 1 : 30(c) 7 : 50(d) 7 : 108 |
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Answer» Answer is : (d) 7 : 108 For first line of Lyman series, n1 = 1 and n2 = 2 \(\therefore\frac{1}{\lambda_1}=R\left(\frac{1}{1^{2}}-\frac{1}{2^{2}}\right)\) \(=R\left(1-\frac{1}{4}\right)=\frac{3R}{4}\) For first line of Paschen series, n1 = 3 and n2 = 4 \(\therefore\frac{1}{\lambda_2}=R\left(\frac{1}{3^{2}}-\frac{1}{4^{2}}\right)\) \(=R\left(\frac{1}{9}-\frac{1}{16}\right)=\frac{7R}{144}\) \(\frac{\lambda_1}{\lambda_2}=\frac{7R}{144}\times\frac{4}{3R}=\frac{7}{108}\) |
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