find the energy density at a point 1m from a 60watt buld .Assume that the efficiency of buld is 20% and it's a point source
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Answered by
1
Answer:
Correct option is
C
4.07Vm
−1
The bulb as a point source ,radiates light in all directions uniformly.
At a distance of 3m, the surface area of the surrounding sphere is
A=4πr
2
=4π(3)
2
=11m
2
Then intensity at this distance is
I=
a
p
=
113
100×2.5
=0.022
m
2
W
Half of this intensity is provided by the electric field and half by the magnetic field
=
2
1
(0.022
m
2
W
)=
2
1
(∈
0
E
rms
2
c)
E
rms
=
[
(8.85×10
−12
×3×10
8
)
(0.222)
]
m
V
=2.9
m
V
E
0
=
2
E
rms
=
2
×2.9V=4.07
m
V
Option C is correct .
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