Question

PHY3

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4. +-14 points TR4 3.P.017 Calculate Amax for blackbody radiation for the following (a) liquid helium (2.5 K) (b) room temperature (293 K) (c) a steel furnace (1450 K) (d) a blue star (8000 K)

Answer 1

4] Use Wein's displacement law relating maximum wavelength emitted and the temperature.

Use Wein's displacement law relating maximum wavelength emitted and the temperature. Lambda_max T = 2.898 times 10^-3 m K So, for T = 25 k[liquid helium] lambda_max = 2.898 times 10^-3/2.5 = 1159.2 mu m T = 293k, lambda_max = 2.898 times 10^-3/293 = 9.89 mu m T = 1450 k, lambda_max = 2.898 times 10^-3/1450 = 1.998 mu m T = 8000K, lambda_max = 2.898 times 10^-3/8000 = 0.362 mu m

a]

So, for T = 2.5 K [liquid helium]

$\lambda_{max} = \frac{2.898\times 10^{-3} }{2.5} = 1159.2 \mu m$

b] T = 293 K,

$\lambda_{max} = \frac{2.898\times 10^{-3} }{293} = 9.89 \mu m$

c] T = 1450 K,

$\lambda_{max} = \frac{2.898\times 10^{-3} }{1450} = 1.998 \mu m$

d] T = 8000 K,

$\lambda_{max} = \frac{2.898\times 10^{-3} }{8000} = 0.362 \mu m$ .