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Question
The magnetic field of a beam emerging from a filter facing a floodlight is given by B0 = 12 × 10–8 sin (1.20 × 107z – 3.60 × 1015t) T. What is the average intensity of the beam?
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Solution
The standard equation of magnetic field can be expressed as B = B0 sin ωt.
We are given equation B = 12 × 10–8 sin (1.20 × 107z – 3.60 × 1015t) T.
On comparing this equation with standard equation, we get
B0 = 12 × 10–8 T
The average intensity of the beam
`I_(av) = 1/2 B_0^2/mu_0 * c = 1/2 xx ((12 xx 10^-8)^2 xx 3 xx 10^8)/(4pi xx 10^-7)`
= 1.71 W/m2
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