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The wavelength of the first Lyman lines ...

The wavelength of the first Lyman lines of hydrogen `He^(+)` and `Li^(2+)` ions and `lamda_(1),lamda_(2)& lamda_(3)` the ratio of these wavelengths is

A

`1:4:9`

B

`9:4:1`

C

`36:9:4`

D

`6:3:2`

Text Solution

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The correct Answer is:
To solve the problem of finding the ratios of the wavelengths of the first Lyman lines of hydrogen (H), helium ion (He⁺), and lithium ion (Li²⁺), we can follow these steps: ### Step 1: Understand the Lyman Series The Lyman series corresponds to electronic transitions in hydrogen-like atoms where an electron falls from a higher energy level (n=2, 3, ...) to the first energy level (n=1). The formula for the wavelength (λ) of the emitted light during these transitions is given by: \[ \frac{1}{\lambda} = R \cdot Z^2 \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right) \] where: - \( R \) is the Rydberg constant, - \( Z \) is the atomic number, - \( n_1 \) is the lower energy level (1 for Lyman series), - \( n_2 \) is the higher energy level (2 for the first line of Lyman series). ### Step 2: Calculate for Each Ion 1. **For Hydrogen (H, Z=1)**: \[ \frac{1}{\lambda_1} = R \cdot 1^2 \left( \frac{1}{1^2} - \frac{1}{2^2} \right) = R \left( 1 - \frac{1}{4} \right) = R \cdot \frac{3}{4} \] Therefore, \[ \lambda_1 = \frac{4}{3R} \] 2. **For Helium Ion (He⁺, Z=2)**: \[ \frac{1}{\lambda_2} = R \cdot 2^2 \left( \frac{1}{1^2} - \frac{1}{2^2} \right) = R \cdot 4 \left( 1 - \frac{1}{4} \right) = R \cdot 4 \cdot \frac{3}{4} = 3R \] Therefore, \[ \lambda_2 = \frac{1}{3R} \] 3. **For Lithium Ion (Li²⁺, Z=3)**: \[ \frac{1}{\lambda_3} = R \cdot 3^2 \left( \frac{1}{1^2} - \frac{1}{2^2} \right) = R \cdot 9 \left( 1 - \frac{1}{4} \right) = R \cdot 9 \cdot \frac{3}{4} = \frac{27R}{4} \] Therefore, \[ \lambda_3 = \frac{4}{27R} \] ### Step 3: Find the Ratios Now we have: - \( \lambda_1 = \frac{4}{3R} \) - \( \lambda_2 = \frac{1}{3R} \) - \( \lambda_3 = \frac{4}{27R} \) To find the ratios \( \lambda_1 : \lambda_2 : \lambda_3 \): - Multiply each wavelength by \( 27R \) to eliminate \( R \): - \( \lambda_1 \cdot 27R = \frac{4 \cdot 27}{3} = 36 \) - \( \lambda_2 \cdot 27R = \frac{1 \cdot 27}{3} = 9 \) - \( \lambda_3 \cdot 27R = \frac{4 \cdot 27}{27} = 4 \) Thus, the ratio is: \[ \lambda_1 : \lambda_2 : \lambda_3 = 36 : 9 : 4 \] ### Final Answer The ratio of the wavelengths of the first Lyman lines of hydrogen, helium ion, and lithium ion is: \[ \boxed{36 : 9 : 4} \]

To solve the problem of finding the ratios of the wavelengths of the first Lyman lines of hydrogen (H), helium ion (He⁺), and lithium ion (Li²⁺), we can follow these steps: ### Step 1: Understand the Lyman Series The Lyman series corresponds to electronic transitions in hydrogen-like atoms where an electron falls from a higher energy level (n=2, 3, ...) to the first energy level (n=1). The formula for the wavelength (λ) of the emitted light during these transitions is given by: \[ \frac{1}{\lambda} = R \cdot Z^2 \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right) \] ...
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