Question

About black body radiation, which one of the following is a WRONG statement?

• A. For all wavelengths, power radiated is same
• B. For shorter wavelengths, radiated power is more
• C. for longer wavelengths, radiated power is less
• D. All wavelengths are emitted by the black body

Hint:

The black body curve has a peak, so power depends on wavelength.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
A black body emits all wavelengths, but not equally. The graph of radiated power against wavelength rises to a peak at a wavelength fixed by the temperature (Wien law), and falls on both sides.

Step 2: Check statement (A):
It says power radiated is the same for all wavelengths. This is wrong, because the curve has a peak and is not flat. So (A) is the WRONG statement.

Step 3: Check statements (B), (C) and (D):
(B) and (C) describe the general trend the question intends: the power is small at long wavelengths and larger towards the shorter wavelengths near the peak. (D) is true because a black body emits every wavelength. All three are accepted as true.

Step 4: Choose:
The wrong statement is (A).

Final Answer:
Radiated power is not the same for all wavelengths. \[ \boxed{A} \]