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JEE Main 26-Aug-2021 Shift 1 Solved Paper
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© examsnet.com
Question : 22
Total: 90
The electric field in a plane electromagnetic wave is given by
E
= 200cos
[
(
0.5
×
10
3
m
)
x
−
(
1.5
×
10
11
rad
s
×
t
)
]
v
m
^
j
If this wave falls normally on a perfectly reflecting surface having an area of
100
cm
2
. If the radiation pressure exerted by the EM wave on the surface during a 10 min exposure is
x
10
9
.
Find the value of x.
[26 Aug 2021 Shift 1]
Your Answer:
Validate
Solution:
The electric field in a plane electromagnetic wave is given by
E
=
200
cos
[
(
0.5
×
10
3
)
x
m
−
(
1.5
×
10
11
rad
s
×
t
)
]
V
m
^
j
∴
E
0
=
200
V
∕
m
Intensity provided by electric field is given by
l
=
1
2
ε
0
E
0
2
C
The radiation pressure exerted by electromagnetic wave on surfaceis given by
P
=
2
l
c
=
2
×
1
2
ε
0
E
0
2
C
c
=
ε
0
E
0
2
P
=
ε
0
E
0
2
=
8.85
×
10
−
12
×
(
200
)
2
=
354
10
9
According to question,
x
10
9
=
354
10
9
∴ x = 354
© examsnet.com
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