The amount of radiation emitted by a perfectly black body is proportional to

CONCEPT:

• Stefan's Law: According to it the radiant energy emitted by a perfectly black body per unit area per sec (i.e. emissive power of black body) is directly proportional to the fourth power of its absolute temperature i.e.
  E ∝ T⁴
  ⇒ E = σT⁴
  Where, is a constant called Stefan’s constant.
• The value of Stefan's constant is 5.67 × 10^-8 W/m²K⁴.

EXPLANATION:

• From above it clear that the amount of radiation emitted by a perfectly black body is proportional to the fourth power of temperature on an ideal gas scale. Thus, option 3 is correct.