The magnetic field an electromangetic wave in a substance is given by ` B = ( 2 xx 10^(-6) T)` cos `[ pi ( 0.04 x+ 10^7 t)]` . Find the electromagnetic wave speed.

Explanation

To find the speed of the electromagnetic wave given the magnetic field equation, we can follow these steps:

### Step 1: Identify the given magnetic field equation
The magnetic field \( B \) is given by:
\[ B = (2 \times 10^{-6} \, T) \cos \left[ \pi (0.04 x + 10^7 t) \right] \]

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