1
JEE Main 2019 (Online) 9th January Evening Slot
+4
-1
The energy associated with electric field is (UE) and with magnetic field is (UB) for an electromagnetic wave in free space. Then :
A
$${U_E} = {{{U_B}} \over 2}$$
B
$${U_E} > {U_B}$$
C
$${U_E} < {U_B}$$
D
$${U_E} = {U_B}$$
2
JEE Main 2019 (Online) 9th January Morning Slot
+4
-1
A plane electromagnetic wave of frequency 50 MHz travels in free space along the positive x-direction. At a particular point in space and time, $$\overrightarrow E = 6.3\widehat j\,V/m.$$ The corresponding magnetic field $$\overrightarrow {B,}$$ at that point will be :
A
18.9 $$\times$$ 10$$-$$8 $$\widehat k$$T
B
2.1 $$\times$$ 10$$-$$8 $$\widehat k$$T
C
6.3 $$\times$$ 10$$-$$8 $$\widehat k$$T
D
18.9 $$\times$$ 108 $$\widehat k$$T
3
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
A plane electromagnetic wave of wavelength $$\lambda$$ has an intensity I. It is propagatting along the positive Y-direction. The allowed expressions for the electric and magnetic fields are givn by :
A
B
C
D
4
JEE Main 2018 (Offline)
+4
-1
An EM wave from air enters a medium. The electric fields are

$$\overrightarrow {{E_1}}$$ = $${E_{01}}\widehat x\cos \left[ {2\pi v\left( {{z \over c} - t} \right)} \right]$$ in air and

$$\overrightarrow {{E_2}}$$ = $${E_{02}}\widehat x\cos \left[ {k\left( {2z - ct} \right)} \right]$$ in medium,

where the wave number k and frequency $$\nu$$ refer to their values in air. The medium is non-magnetic. If $${\varepsilon _{{r_1}}}$$ and $${\varepsilon _{{r_2}}}$$ refer to relative permittivities of air and medium respectively, which of the following options is correct ?
A
$${{{\varepsilon _{{r_1}}}} \over {{\varepsilon _{{r_2}}}}} = 4$$
B
$${{{\varepsilon _{{r_1}}}} \over {{\varepsilon _{{r_2}}}}} = 2$$
C
$${{{\varepsilon _{{r_1}}}} \over {{\varepsilon _{{r_2}}}}} = {1 \over 4}$$
D
$${{{\varepsilon _{{r_1}}}} \over {{\varepsilon _{{r_2}}}}} = {1 \over 2}$$
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