A plane electromagnetic wave, has frequency of 2.0 × 1010 Hz and its energy density is 1.02 × 10-8 J / m 3 in vacuum. The amplitude of the magnetic field of the wave is close to ((1/4 π ε0)=9 × 109 ( Nm 2/ C 2). and speed of light .=3 × 108 ms -1):

Question

A plane electromagnetic wave, has frequency of 2.0 × 1010 Hz and its energy density is 1.02 × 10-8 J / m 3 in vacuum. The amplitude of the magnetic field of the wave is close to ((1/4 π ε0)=9 × 109 ( Nm 2/ C 2). and speed of light .=3 × 108 ms -1): (A) 180 nT (B) 160 nT (C) 150 nT (D) 190 nT

Tardigrade Admin · Accepted Answer

Energy density ( dU / dV )=( B 02/2 μ0) 1.02 × 10-8=( B 02/2 × 4 π × 10-7) B 02=(1.02 × 10-8) ×(8 π × 10-7) B 0=16 × 10-8 T =160 nT

$180 n T$

$160 n T$

$150 n T$

$190 n T$

Energy density $\frac{d U}{d V} = \frac{B _{0}^{2}}{2 μ _{0}}$
$1.02 \times 1 0^{- 8} = \frac{B _{0}^{2}}{2 \times 4 π \times 1 0 ^{- 7}}$
$B_{0}^{2} = (1.02 \times 1 0^{- 8}) \times (8 π \times 1 0^{- 7})$
$B_{0} = 16 \times 1 0^{- 8} T = 160 n T$

Q. A plane electromagnetic wave, has frequency of 2.0×1010Hz and its energy density is 1.02×10−8J/m3 in vacuum. The amplitude of the magnetic field of the wave is close to (4πε0​1​=9×109C2Nm2​ and speed of light =3×108ms−1):

180nT

160nT

150nT

190nT

Energy density dVdU​=2μ0​B02​​ 1.02×10−8=2×4π×10−7B02​​ B02​=(1.02×10−8)×(8π×10−7) B0​=16×10−8T=160nT

$180 n T$

$160 n T$

$150 n T$

$190 n T$

Energy density $\frac{d U}{d V} = \frac{B _{0}^{2}}{2 μ _{0}}$
$1.02 \times 1 0^{- 8} = \frac{B _{0}^{2}}{2 \times 4 π \times 1 0 ^{- 7}}$
$B_{0}^{2} = (1.02 \times 1 0^{- 8}) \times (8 π \times 1 0^{- 7})$
$B_{0} = 16 \times 1 0^{- 8} T = 160 n T$