Question

A plane electromagnetic wave travels through a medium and the magnetic field associated with it is given by \[ B = 5 \times 10^{-8} \sin (3 \times 10^{10} t - 150 x) \text{ T} \] where \(x\) is in metres and \(t\) is in seconds. The velocity of the wave is :

• A. \(2\cdot0 \times 10^8\text{ ms}^{-1}\)
• B. \(4\cdot5 \times 10^7\text{ ms}^{-1}\)
• C. \(3\cdot5 \times 10^7\text{ ms}^{-1}\)
• D. \(2\cdot5 \times 10^8\text{ ms}^{-1}\)

Hint:

For any wave equation expressed in terms of \(( \omega t - kx )\), the wave speed is always equal to the coefficient of \(t\) divided by the coefficient of \(x\). This rule allows you to quickly solve wave speed problems without needing to memorize secondary relations.

Answer 1

The Correct Option is A