Which discovery did Joseph Fraunhofer make regarding the elements that make up the universe?

• A. He identified the periodic law, organizing elements by increasing atomic number.
• B. He observed dark absorption lines in the solar spectrum, indicating that elements absorb specific wavelengths of light.
• C. He discovered the electron as a fundamental particle in atoms.
• D. He proposed that atoms are indivisible and cannot be broken down further.

Answer: (B)

Verified step by step guidance

1. Understand the historical context: Joseph Fraunhofer was a physicist and optician known for his work with light and spectra in the early 19th century.
2. Recognize that Fraunhofer's key contribution was related to the study of sunlight and its spectrum, where he observed specific dark lines, now called Fraunhofer lines.
3. These dark absorption lines occur because elements in the Sun's atmosphere absorb light at particular wavelengths, which means each element has a unique spectral fingerprint.
4. This discovery was fundamental because it showed that elements could be identified by the specific wavelengths of light they absorb, linking light absorption to elemental composition.
5. Note that Fraunhofer did not identify the periodic law, discover the electron, or propose atomic indivisibility; his main discovery was the observation of dark absorption lines in the solar spectrum.