A laser beam has intensity of 4.0 × 10^ 14 ~W / m^ 2 . The amplitude of magnetic field associated with beam is \_\_\_\_ T. (Take _ o =8.85 × 10^ -12 C^ 2 / Nm^ 2 and c=3 × 10^ 8 ~m / s )

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Quantrex Academy · Accepted Answer

Correct answer: B. 1.83

The intensity of an electromagnetic wave is

I = \frac{1}{2} \epsilon_0 c E_0^2

.
From the relation

E_0 = c B_0

, we get

I = \frac{1}{2} \epsilon_0 c^3 B_0^2

.
Solving for magnetic field amplitude:

B_0 = \sqrt{\frac{2I}{\epsilon_0 c^3}} = \sqrt{\frac{2 \times 4.0 \times 10^{14}}{8.85 \times 10^{-12} \times (3 \times 10^8)^3}} = \sqrt{\frac{8.0 \times 10^{14}}{2.39 \times 10^{14}}}

= \sqrt{3.347} = 1.83

T.

A laser beam has intensity of 4.0 × 10^ 14 ~W / m^ 2 . The...

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