Question

Bohr's second postulate implies quantisation of

• A. Charge of an electron
• B. Energy of an electron
• C. Angular momentum of electron
• D. Radiated energy by an electron

Hint:

Remember the formula \( L = n\hbar \), where \( \hbar = \frac{h}{2\pi} \). This postulate was later explained by de-Broglie's hypothesis of matter waves, showing that only certain orbits can accommodate a standing wave of the electron.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question refers to the specific physical quantity that is quantized according to Bohr's second postulate in his atomic model of hydrogen.
Step 3: Detailed Explanation:
Bohr's second postulate (also known as the quantum condition) states that an electron can revolve around the nucleus only in those fixed circular orbits for which its orbital angular momentum (\( L \)) is an integral multiple of \( \frac{h}{2\pi} \), where \( h \) is Planck's constant.
Mathematically, this is expressed as:
\[ L = mvr = \frac{nh}{2\pi} \]
where \( n = 1, 2, 3, \dots \) is the principal quantum number. This implies that angular momentum is not continuous but exists in discrete "packets" or quanta.
Step 4: Final Answer:
Bohr's second postulate implies the quantisation of angular momentum of an electron, which corresponds to option (3).