Question:

Two spheres of the same material have radii $ 1 \,m $ and $ 4\, m $ and temperatures $ 4000\, K $ and $ 2000\, K $ respectively., The ratio of energy radiated per second by the first sphere to the second is

Updated On: May 5, 2023
  • $ 1 : 1 $
  • $ 16 : 1 $
  • $ 4 : 1 $
  • $ 1 : 9 $
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The Correct Option is A

Solution and Explanation

Energy radiated per second by a body which has surface area $A$ at temperature $T$ is given by Stefan's law, $E = \sigma AT^4$ Therefore $\frac{E_{1}}{E_{2}} = \left(\frac{r_{1}}{r_{2}}\right)^{2}\left(\frac{T_{1}}{T_{2}}\right)^{4}$ $ = \left(\frac{1}{4}\right)^{2}\left(\frac{4000}{2000}\right)^{4}$ $ \frac{E_{1}}{E_{2}} = \frac{16}{16} = \frac{1}{1}$
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Concepts Used:

Radiation

Radiation is the energy or particles from a source that travels from one media to other. It travels through a medium after its emission from a source and is absorbed by matter.

Forms of Radiation:

  1. Particle Radiation includes the alpha (α), beta (β), and neutron radiations.
  2. Gravitational Radiation includes the radiation that takes the form of gravitational waves or as ripples in the curvature of space-time.
  3. Acoustic Radiation includes ultrasound, seismic and sound waves.
  4. Electromagnetic Radiation is inclusive of radio waves, gamma radiation (γ), x-rays, and visible light.

Types of Radiation:

  • Ionizing Radiation - It carries more than 10 eV, that is enough to ionize atoms and molecules and break chemical bonds.
  • Non-ionizing Radiation – It consists of alpha particles, beta particles, and gamma particles, whereas ionizing radiation consists of microwave radiation, infrared radiation and radio waves.

Read More: Types of Radiation