Question

In semiconductors, at room temperature the

• A. valance band is partially empty and the conduction band is partially filled.
• B. valance band is completely filled and the conduction band is partially filled.
• C. valance band is completely filled.
• D. conduction band is completely empty.

Hint:

Thermal energy lifts a few electrons from the valence band to the conduction band.

Answer 1

The Correct Option is A

Step 1: Elimination
A completely filled valence band or a completely empty conduction band is true only at $0\ \text{K}$, so options (C) and (D) do not hold at room temperature.

Step 2: Check Option B
A full valence band with a partially filled conduction band is incomplete, since excited electrons leave holes behind.

Step 3: Conclusion
Option (A) describes both bands correctly.

Final Answer:
Both bands are partially occupied at room temperature. \[ \boxed{\text{(A) }\text{valance band is partially empty and the conduction band is partially filled}} \]