The minimum temperature of a body at which it emits visible light is approximately.......$^oC$.

Two identical balls $A$ and $B$ are heated. Ball $A$ appears blue and ball $B$ appears red. What is the relationship between their temperatures?

$A$ black body is at a temperature of $5780 \text{ K}$. The energy of radiation emitted by the body at wavelength $300 \text{ nm}$ is $U_1$, at wavelength $500 \text{ nm}$ is $U_2$, and at wavelength $900 \text{ nm}$ is $U_3$. Wien's constant $b = 2.89 \times 10^6 \text{ nm K}$. This shows that:

The temperature of a black body is $2880 \, K$. $U_1$ is the energy of radiation between $499 \, nm$ and $500 \, nm$,$U_2$ is the energy of radiation between $999 \, nm$ and $1000 \, nm$,and $U_3$ is the energy of radiation between $1499 \, nm$ and $1500 \, nm$. Given Wien's constant $b = 2.88 \times 10^6 \, nm \cdot K$,which of the following is correct?

The following graph represents the radiant power versus wavelength of a black body. The area under the curve represents:

The surface temperature of the sun which has maximum energy emission at $500 \,nm$ is $6000 \,K$. The temperature of a star which has maximum energy emission at $400 \,nm$ will be: (in $\,K$)