Radiation

According to Stefan�s law, amount of radiations emitted , Percentage increase in

According Stefan's law, emission rate of a ideal blackbody For ...(i) For ...(ii) From Eqs. (i) and (ii), Hence,

Step 1: Understanding the Concept:
Wien's displacement law: .

Step 2: Detailed Explanation:

Given

Temperature must be increased to .

Step 3: Final Answer:
Temperature should be increased to .

Step 1: Understanding the Concept:
Electromagnetic radiation carries momentum. When it strikes a surface, it exerts a force, and consequently a pressure, called radiation pressure. The magnitude depends on the intensity of the radiation and whether the surface absorbs or reflects it.

Step 2: Key Formula or Approach:
"Energy per unit area per unit time" is the definition of Intensity ( ).
For a perfectly absorbing surface, the radiation pressure ( ) is given by:

Where is the speed of light in vacuum.

Step 3: Detailed Explanation:
Given:
Intensity, J/(m s) = W/m
Speed of light, m/s
Substitute these values into the formula:



Step 4: Final Answer:
The radiation pressure is N/m .

Step 1: Understanding the Concept:
Radiation pressure is defined exactly as the physical force exerted by electromagnetic radiation per unit area on a given target.
For a massive spherical body like the Earth absorbing radiation from a distant source (the Sun), the effective intercepting area is not the total surface area of the sphere, but rather its flat projected cross-sectional area.
Step 2: Key Formula or Approach:
The defining formula for pressure based on applied force and intercepting area is .
The effective intercepting cross-sectional area of a sphere of radius is exactly a circle: .
Step 3: Detailed Explanation:
The total force exerted by the solar radiation is given directly as .
The given radius of the Earth is .
First, calculate the effective cross-sectional area intercepting the light:
Now, directly substitute the force and the calculated area into the radiation pressure formula:
Step 4: Final Answer:
The calculated radiation pressure acting on the Earth is approximately .