A point source emits electromagnetic waves isotropically with an average power of 60 W . The amplitude of the electric field at a distance of 3 m from the source is: (Given c = 3 10^8 m s ⁻¹ and ₀ = 4 10⁻⁷ T m A ⁻¹ )

Step-by-step solution

The intensity I of the electromagnetic wave at a distance r from an isotropic point source is given by the power divided by the surface area of a sphere of radius r : I = P 4 r^2 Substituting the given values: I = 60 4 (3)^2 = 60 36 = 5 3 W m ⁻² The intensity is also related to the amplitude (peak value) of the electric field E₀ by the relation: I = E₀^2 2 ₀ c Equating the two expressions for intensity: E₀^2 2 ₀ c = 5 3 E₀^2 = 5 3 2 ₀ c Substituting the values of ₀ and c : E₀^2 = 5 3 2 (4 10⁻⁷) (3 10^8) E₀^2 = 5 3