Question

given the 5 watt source coming in from 2π/3 solid angle of a radius 3 meters the corresponding source of energy carried by the ray is

a.5/4π2
b.1/2π2
c.π2
d.1​

Answer 1

Answer:

the answers of your questions is ( a)

Answer 2

Answer:

Energy radiated by the source is  $\frac{5}{4\pi ^{2} }$  $W/m^{2}$. Option a. is correct.

Explanation:

• Energy radiated by a source is equal to power per unit area per unit solid angle.
• The solid angle is called $steradians$. This is the angle subtended at the sphere center by a certain area surface.
• For a sphere the solid angle is $4\pi$ $steradians$.

The formula for energy carried is given by:

$E=\frac{P}{SA}$

where $P$ is the power of source

           $S$ is the subtended solid angle.

           $A$ is subtended area.

Step 1:

Given source power, $P=5$ $watt$

Subtended solid angle, $S=\frac{2\pi }{3}$ $steradians$

Subtended area, $A=(\frac{2\pi }{3} )*(radius)^{2}$

                                 $=\frac{2\pi }{3} *3^{2}$ $m^{2}$

Step 2:

Energy radiated by the source  $= \frac{5 W}{\frac{2\pi }{3}*\frac{2\pi }{3} *9}$  $W/m^{2}$

                                                    $=\frac{5}{4\pi ^{2} }$  $W/m^{2}$

So, energy radiated by the source is  $\frac{5}{4\pi ^{2} }$  $W/m^{2}$.

Option a. is correct.