Question

When an electron in hydrogen atom revolves in a stationary orbit, it

• A. does not radiate light though its velocity changes
• B. does not radiate light and velocity remains unchanged
• C. radiates light but its velocity is unchanged
• D. radiates light with the change of energy

Hint:

By Bohr's postulate a stationary orbit does not radiate, but motion in a circle still changes the direction of velocity.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Bohr's first postulate says an electron in a stationary orbit does not radiate energy.

Step 2: Radiation
Light is emitted only when the electron jumps between orbits, so there is no radiation while it stays in one orbit.

Step 3: Velocity
The electron moves in a circle, so the direction of its velocity changes continuously even though its speed is constant.
Hence the velocity changes.

Step 4: Compare the options
No radiation with a changing velocity matches option (A).

Final Answer:
The electron does not radiate, though its velocity changes. \[ \boxed{\text{(A) }\text{does not radiate light though its velocity changes}} \]