What is the wavelength of light that is emitted when an excited electron in the hydrogen atom falls from [tex]n=5[/tex] to [tex]n=1[/tex]?

A. [tex]9.12 \times 10^{-8} m[/tex]
B. [tex]9.50 \times 10^{-8} m[/tex]
C. [tex]1.05 \times 10^7 m[/tex]
D. [tex]2.09 \times 10^{-18} m[/tex]



Answer :

To determine the wavelength of light emitted when an electron in a hydrogen atom transitions from the energy level [tex]\(n=5\)[/tex] to [tex]\(n=1\)[/tex], we can use the Rydberg formula for hydrogen:

[tex]\[ \frac{1}{\lambda} = R \left( \frac{1}{n_f^2} - \frac{1}{n_i^2} \right) \][/tex]

Where:
- [tex]\(\lambda\)[/tex] is the wavelength of the emitted light,
- [tex]\(R\)[/tex] is the Rydberg constant (approximately [tex]\(1.097373 \times 10^7 \, \text{m}^{-1}\)[/tex]),
- [tex]\(n_i\)[/tex] is the initial energy level (in this case, [tex]\(n_i = 5\)[/tex]),
- [tex]\(n_f\)[/tex] is the final energy level (in this case, [tex]\(n_f = 1\)[/tex]).

Let's plug in the given values:

[tex]\[ R \approx 1.097373 \times 10^7 \, \text{m}^{-1} \][/tex]
[tex]\[ n_i = 5 \][/tex]
[tex]\[ n_f = 1 \][/tex]

Using these values in the Rydberg formula, the equation becomes:

[tex]\[ \frac{1}{\lambda} = 1.097373 \times 10^7 \left( \frac{1}{1^2} - \frac{1}{5^2} \right) \][/tex]

First, calculate the terms inside the parentheses:

[tex]\[ \frac{1}{1^2} = 1 \][/tex]
[tex]\[ \frac{1}{5^2} = \frac{1}{25} = 0.04 \][/tex]

So,

[tex]\[ \frac{1}{\lambda} = 1.097373 \times 10^7 \left( 1 - 0.04 \right) = 1.097373 \times 10^7 \times 0.96 \][/tex]

Next, calculate the product:

[tex]\[ \frac{1}{\lambda} \approx 1.05347808 \times 10^7 \, \text{m}^{-1} \][/tex]

Taking the reciprocal to find [tex]\(\lambda\)[/tex]:

[tex]\[ \lambda \approx \frac{1}{1.05347808 \times 10^7} \approx 9.4923651 \times 10^{-8} \, \text{m} \][/tex]

Thus, the wavelength of light that is emitted is approximately [tex]\(9.492 \times 10^{-8} \, \text{m}\)[/tex].

Among the given options, the closest value to this result is:

[tex]\[ \boxed{9.50 \times 10^{-8} \, \text{m}} \][/tex]