Answer:
3622.5 K
Explanation:
The radiation of red giant star is 800nm.
We need to find the surface temperature of the star. Let it is T.
Using Wein's displacement law to find it as follows :
[tex]\lambda=\dfrac{C}{T}[/tex]
C is constant an T is temperature
[tex]T=\dfrac{C}{\lambda}\\\\T=\dfrac{2.898\times 10^{-3}}{800\times 10^{-9}}\\\\ T=3622.5\ K[/tex]
So, the surface temperature of the star is 3622.5 K.