Three discs A, B and C having radii 2; m, 4;m, and 6 ;m, respectively are coated with carbon black on their outer surfaces. The

Q: Three discs $A, B$ and $C$ having radii $2\; m, 4\;m,$ and $6 \;m$, respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are $300\; nm, 400\; nm$ and $500\; nm$, respectively. The power radiated by them are $Q_A,Q_B$ and $Q_C$ respectively.

b (b) Radiated power$P = A\varepsilon \sigma {T^4}$ ==> P$ \propto A{T^4}$ From Wein’s law, ${\lambda _m}T = $constant ==> $T \propto \frac{1}{{{\lambda _m}}}$ $P \propto \frac{A}{{{{({\lambda _m})}^4}}} \propto \frac{{{r^2}}}{{{{({\lambda _m})}^4}}}$ ==> ${Q_A}:{Q_B}:{Q_C} = \frac{{{2^2}}}{{{{(300)}^4}}}:\frac{{{4^2}}}{{{{(400)}^4}}}:\frac{{{6^2}}}{{{{(500)}^4}}}$ ${Q_B}$ will be maximum.

SECTION - A [PHYSICS - MCQ]

GSEB - English Medium

Three discs $A, B$ and $C$ having radii $2\; m, 4\;m,$ and $6 \;m$, respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are $300\; nm, 400\; nm$ and $500\; nm$, respectively. The power radiated by them are $Q_A,Q_B$ and $Q_C$ respectively.

A$Q_a$ is maximum
B$Q_b$ is maximum
C$Q_c$ is maximum
D$Q_a$ = $Q_b$ = $Q_c$

IIT 2004, Diffcult

STD 11 Science
NEET
STD 11 - 10.2. transmission of heat
Physics

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