Assuming that a given star radiates like a blackbody, estimate the wavelength of its strongest radiation when it emits a total intensity of 375 MWm? (b) Find the temperature at its surface.

Respuesta :

Answer:

a) wavelength, [tex]\lambda _{maximum} = 3.214\times 10^{-7} m[/tex]

b) Surface temperature, T = 9017.89 K

Given:

Total Intensity, P = 375 MWm = 375[tex]\times 10^{6} Wm[/tex]

Here, total intensity is the power per unit area

Solution:

a) Using Wien's displacement law which gives the inverse relation between temperature and wavelength for black body radiation and is given by:

[tex]\lambda _{maximum} = \frac{k}{T}[/tex]               (1)

where

k = proportionality constant = 2898 [tex]\micro m.K[/tex]

[tex]\lambda _{maximum}[/tex] = maximum wavelength

T = Temperature in kelvin

From eqn (1):

[tex]\lambda _{maximum} = \frac{2898\times 10^{-6}}{T}[/tex]           {2}

b) Temperature, T at the surface is given by Stefan-Boltzman law:

P = [tex]\sigma T^{4}[/tex]                                 (3)

where

[tex]\sigma = Stefan-Boltzman = 5.670373\times 10^{-8} W/m^{2}K^{4}[/tex]

Using eqn (3):

[tex]T^{4} = \frac{P}{\sigma }[/tex]

[tex]T^{4} = \frac{375\times 10^{6}}{5.670373\times 10^{-8}} = 6.61332\times 10^{15}[/tex]

T = 9017.89 K

Now, substituting the value of T = 9017.89 K in eqn (2):

[tex]\lambda _{maximum} = \frac{2898\times 10^{-6}}{9017.89} = 3.214\times 10^{-7} m[/tex]

[tex]\lambda _{maximum} = 3.214\times 10^{-7} m[/tex]