Consider a blackbody that radiates with an intensity i1 at a room temperature of 300 k. at what intensity i2 will this blackbody radiate when it is at a temperature of 400 k?

I₂ = 3.16 I₁

Explanation:

A blackbody is a substance that absorbs radiation of all wavelengths and radiates in a continuous spectrum at all wavelengths. It is given the name blackbody because an object that absorbs light at all wavelengths appears black to the human eye.

The total intensity I (the average rate of radiation of energy per unit surface area) emitted from a blackbody was shown to be proportional to the fourth power of its temperature:

I = бT⁴.

This is called the Stefan-Boltzmann law for a blackbody. The constant of proportionality sigma is known as the Stefan-Boltzmann constant.

So, I is directly proportional to T⁴

∴ I₂/I₁ = T⁴₂/T⁴₁

         =400⁴/300⁴ = 3.16

So, I₂ = 3.16 I₁

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

wavelegth as in spectrum red oygbiv