Question

A plane electromagnetic wave travels through a medium and the magnetic field associated with it is given by

B = 5 × 10⁻⁸ sin (3 × 10¹⁰ t − 150 x)T

where x is in metres and t is in seconds. 

The velocity of the wave is:

Options

• 2.0 × 10⁸ ms⁻¹

• 4.5 × 10⁷ ms⁻¹

• 3.5 × 10⁷ ms⁻¹

• 2.5 × 10⁸ ms⁻¹

Answer 1

2.0 × 10⁸ ms⁻¹

Explanation:

A plane wave is written as:

sin(ωt − kx)

B = 5 × 10⁻⁸ sin(3 × 10¹⁰ t − 150 x)

ω = 3 × 10¹⁰

k = 150

`v = ω/k`

= `(3 xx 10^10)/150`

= 2.0 × 10⁸ ms⁻¹