Astrophysics question

Question

Object A emits most strongly at 400 nm, while object B emits most strongly at 800 nm. What can we say about their relative temperatures?

A’s temperature is the same as B’s.
Nothing. Temperature is related to brightness, not emitted wavelength.
A’s temperature is twice as high as B’s.
B’s temperature is twice as high as A’s.

 

 

 

Cooler stars (about 3000 K) emit most of their radiation at wavelengths shorter than 600 nm.
True
False

Answer 1

According to Wien's displacement law,

 

λ_maxT = c, c = a constant

 

Then

 

T = c/λ_max

 

Therefore, the body with lower λ_max is hotter.  In this case we have

 

T_A = c/400

T_B = c/800

 

Then T_A = 2T_B.  A’s temperature is twice as high as B’s.

 

The second question is false. Cooler stars emit primarily at longer wavelengths.