The absorption spectrum of sodium has a line at 589 nm. What is the energy of this line? (The speed of light in a vacuum is [tex]\(3.00 \times 10^8 \, \text{m/s}\)[/tex], and Planck's constant is [tex]\(6.626 \times 10^{-34} \, \text{J} \cdot \text{s}\)[/tex].)

A. [tex]\(2.96 \times 10^{18} \, \text{J}\)[/tex]
B. [tex]\(8.89 \times 10^{26} \, \text{J}\)[/tex]
C. [tex]\(3.37 \times 10^{-19} \, \text{J}\)[/tex]
D. [tex]\(5.09 \times 10^{14} \, \text{J}\)[/tex]



Answer :

Let's solve the problem step by step.

### Given Data:
- Wavelength of sodium absorption line, [tex]\(\lambda = 589 \, \text{nm}\)[/tex]
- Speed of light in a vacuum, [tex]\(c = 3.00 \times 10^8 \, \text{m/s}\)[/tex]
- Planck's constant, [tex]\(h = 6.626 \times 10^{-34} \, \text{J} \cdot \text{s}\)[/tex]

### Step-by-Step Solution:

1. Convert the wavelength from nanometers to meters:
- [tex]\(1 \, \text{nm} = 10^{-9} \, \text{m}\)[/tex]
- [tex]\(\lambda = 589 \, \text{nm} = 589 \times 10^{-9} \, \text{m} = 5.89 \times 10^{-7} \, \text{m}\)[/tex]

2. Calculate the frequency ([tex]\( \nu \)[/tex]) of the light using the formula:
[tex]\[ \nu = \frac{c}{\lambda} \][/tex]
- Plug in the values:
[tex]\[ \nu = \frac{3.00 \times 10^8 \, \text{m/s}}{5.89 \times 10^{-7} \, \text{m}} \][/tex]
- Solving for [tex]\(\nu\)[/tex]:
[tex]\[ \nu = 5.0933786078098475 \times 10^{14} \, \text{Hz} \][/tex]

3. Calculate the energy (E) of the photon using Planck's equation:
[tex]\[ E = h \nu \][/tex]
- Plug in the values:
[tex]\[ E = (6.626 \times 10^{-34} \, \text{J} \cdot \text{s}) \times (5.0933786078098475 \times 10^{14} \, \text{Hz}) \][/tex]
- Solving for [tex]\(E\)[/tex]:
[tex]\[ E = 3.374872665534805 \times 10^{-19} \, \text{J} \][/tex]

### Conclusion:
The energy of the sodium absorption line at [tex]\(589 \, \text{nm}\)[/tex] is approximately:
[tex]\[ 3.37 \times 10^{-19} \, \text{J} \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{3.37 \times 10^{-19} \, \text{J}} \][/tex]
Which corresponds to option C.

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