Question

Out of the following, which statement is NOT true about black body radiation ?

• A. Intensity is more for shorter wavelengths (\(λ\)).
• B. Intensity is same for all wavelengths (\(λ\)).
• C. Intensity is less for longer wavelengths (\(λ\)).
• D. A black body emits all wavelengths (\(λ\)).

Hint:

The spectrum of a black body is a curve with a peak: intensity depends on wavelength and is not flat.

Answer 1

The Correct Option is B

Step 1: Think of the graph
The graph of intensity versus wavelength for a black body is a hump-shaped curve, not a horizontal line.

Step 2: Wien and Planck
The hump moves toward shorter wavelengths as temperature rises. This shows that the intensity depends on the wavelength.

Step 3: Evaluate statement (B)
A horizontal line would mean equal intensity at every wavelength, which would give infinite total energy. This contradicts both the measured curve and Planck's law, so (B) is not a true statement.

Step 4: Answer
Option (B).

Final Answer:
Statement (B) is not true. This is option (B). \[ \boxed{\text{(B) }\text{Intensity is same for all wavelengths}} \]