Question

Parallel rays of light of intensity I = 912 Wm are incides
on a spherical black body kept in surroundings of
temperature 300K. Take Stefan-Boltzmann constant
o=5.7x10 - WMK and assume that the energy
exchange with the surroundings is only through radiation
The final steady state temperature of the black body is close
to:
(JEE (Advanced) 2014)
(a) 330 K
(b) 660 K
(c) 990 K
(d) 1550 K​

Answer 1

Answer:

(a) 330 k

Explanation:

Stefan's law,

Note here,

Answer 2

Question:

Parallel rays of light of intensity I = 912 Wm are incides on a spherical black body kept in surroundings of temperature 300K. Take Stefan-Boltzmann constant o=5.7x10 - WMK and assume that the energy exchange with the surroundings is only through radiation The final steady state temperature of the black body is close to: (JEE (Advanced) 2014)

(a) 330 K (b) 660 K (c) 990 K (d) 1550 K​

Solution:

During steady state, From Stefan-Boltzmann law, we know,

IπR²  = σ ( T'^4 - T^4)4πR²

or, I =σ (T'4 – 4T )^ 4

or, T'^4 – 4T = 40 × 10^8

or,T'^4 – 81 × 10^8 = 40 ×10^8

or,T'^4 = 121 ×10^8

or, T'≈ 330 K

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