Radiation

Step 1: Stefan’s law.
E T⁴

Step 1: Use the thermal conductivity equation.
The heat conducted through both rods is the same, so we use the formula for thermal conductivity , where is the thermal conductivity, is the area, is the length, and , are the temperatures at each end.
Step 2: Set up the equation for the temperature at the junction.
Equating the heat conducted through copper and steel, we find the temperature at the junction to be 10.6°C. Final Answer:

Step 1: Use the Stefan-Boltzmann law.
The power emitted by a black body is given by the Stefan-Boltzmann law: , where is the surface area of the star, and is the temperature.
Step 2: Solve for .
Rearranging the equation for , we get . Final Answer:

Step 1: According to Wien’s displacement law:
Step 2: Wavelength depends only on temperature, not on nature or area.