Question

Problems 6.14

(a) At what wavelength does the continuous spectrum from sunspots peak?

(b) What is the ratio of intensities at 550 nm in a sunspot and in the normal photosphere?

(c) What is the ratio of energy per second per surface area

Answer 1

a) using the wien's displacement law,

Wavelength max = b/T ,where b= 2900 \mum.K & T= temperature in K.

Considering,the surface temperature of sunspot to be 4000K,

Wavelength max= 2900 *10^(-6)/4000 = 7.22 × 10^(-7) m.

b) to know the ratio of intensities at 550nm ,the energy distribution in sunspot spectrum should be known.

c)ratio of energies= (ratio of temperatures)^4

From Stephan Boltzmann law,

Ratio of energies = (temperature of sunspot/temperature of sun surface)^4

Ratio of energies =(4000/5800)^4 = 0.22621