Question

The star Rigel in the constellation Orion (the Hunter) emits its greatest intensity of radiation at a wavelength of 239 nm.

a) Calculate the surface temperature of the star.

b) What colour is the star? Explain your answer.

Answer 1

a) Solution :

From Wien's displacement law T = constant = 0.0029 mK

where = wavelength of greatest intensity of radiation = 239 nm = 239 x 10 ^-9 m

and T = surface temperature in kelvin (K)

so T = 0.0029 / = 0.0029 /(239 x 10 ^-9 ) =

so surface temperature of the star

Answer:

b) Solution:

As = 239 nm so the star cannot be seen with bare  eyes  ( visible range 380nm to 740nm )

as the wavelenght of the star lies in ultraviolet region (10 nm to 400 nm ) So the colour of the star is ultraviolet ( which cannot be seen with bare eyes)

Answer : Ultraviolet.

Thank You.