A point source radiates energy at the rate of 10 Joules per second, or 10 Watts. As shown in the diagram, two spherical shells of radii r1 and r2 (r1 < r2) receive energies E1 and E2 per second, respectively. Which of the following option(s) is/are true?
A point source radiates energy at the rate of 10 Joules per second, or 10 Watts. As shown in the diagram, two spherical shells of radii r1 and r2 (r1 < r2) receive energies E1 and E2 per second, respectively. Which of the following option(s) is/are true?
The correct option is D Energy from a point source spreads out isotropically in all directions.
The diagram shows a point source radiating energy at 10 Watts, or 10 Joules every second. This energy spreads out equally in all directions (isotropically), and travels at the constant speed of light. This can be imagined as a spherical shell of energy centered at the source, expanding at the wave speed of (speed of light), just like circular waves travelling outwards when you drop a pebble on calm waters.
As the spherically distributed energy expands around the point source, it will deliver the same energy to a sphere of radius r2 as it will deliver to a sphere of radius r2 . Hence, option D is correct, which implies option B should also be correct.
Energy from a point source spreads out isotropically in all directions.
The diagram shows a point source radiating energy at 10 Watts, or 10 Joules every second. This energy spreads out equally in all directions (isotropically), and travels at the constant speed of light. This can be imagined as a spherical shell of energy centered at the source, expanding at the wave speed of (speed of light), just like circular waves travelling outwards when you drop a pebble on calm waters.
As the spherically distributed energy expands around the point source, it will deliver the same energy to a sphere of radius r2 as it will deliver to a sphere of radius r2 . Hence, option D is correct, which implies option B should also be correct.
