Exam 31: Electromagnetic Fields and Waves

If a beam of electromagnetic radiation has an intensity of 120 W/m²,what is the maximum value of the electric field? (c = 3.0 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A, ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

A radiometer has two square vanes (1.0 cm by 1.0 cm),attached to a light horizontal cross arm,and pivoted about a vertical axis through the center,as shown in the figure.The center of each vane is 6.0 cm from the axis.One vane is silvered and it reflects all radiant energy incident upon it.The other vane is blackened and it absorbs all incident radiant energy.An electromagnetic wave with an intensity of 0.30 kW/m² is incident normally upon the vanes.What is the torque due to radiation pressure on the vane assembly about the vertical axis? (c = 3.00 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A,ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

A sinusoidal electromagnetic wave in vacuum delivers energy at an average rate of 5.00 µW/m².What are the amplitudes of the electric and magnetic fields of this wave? (c = 3.0 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A,ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

The energy per unit volume in an electromagnetic wave is

An electromagnetic wave propagates along the +y direction as shown in the figure.If the electric field at the origin is along the +z direction,what is the direction of the magnetic field?

A planar electromagnetic wave is propagating in the +x direction.At a certain point P and at a given instant,the electric field of the wave is given by = (0.082 V/m) .What is the Poynting vector at the point P at that instant? (c = 3.0 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A, ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

A radiometer has two square vanes (each measuring 1.0 cm by 1.0 cm),attached to a light horizontal cross arm,and pivoted about a vertical axis through the center,as shown in the figure.The center of each vane is 6.0 cm from the axis.One vane is silvered and it reflects all radiant energy incident upon it.The other vane is blackened and it absorbs all incident radiant energy.An electromagnetic wave with an intensity of 0.30 kW/m² is incident normally upon the vanes.What is the electromagnetic power absorbed by the blackened vane? (c = 3.00 × 10⁸ m/s, μ₀ = 4π × 10^-7 T ∙ m/A,ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

If the z-component of the magnetic field of an electromagnetic wave traveling in the +x direction through vacuum obeys the equation B_z(x,t)= (1.25 μT)cos[(3800 m^-1)x - (1.14 × 10-¹² rad/s)t],what is the largest that the y component of the electric field can be? (c = 3.0 × 10⁸ m/s)

When an electromagnetic wave falls on a white,perfectly reflecting surface,it exerts a force F on that surface.If the surface is now painted a perfectly absorbing black,what will be the force that the same wave will exert on the surface?

Polarized light passes through a polarizer.If the electric vector of the polarized light is horizontal what,in terms of the initial intensity I₀,is the intensity of the light that passes through a polarizer if the polarizer is tilted 22.5° from the horizontal?

An 800-kHz radio signal is detected at a point 2.7 km distant from a transmitter tower.The electric field amplitude of the signal at that point is 0.36 V/m.Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed.What is the intensity of the radio signal at that point? (c = 3.00 × 10⁸ m/s, μ₀ = 4π × 10^-7 T ∙ m/A,ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

If the intensity of an electromagnetic wave is 80 MW/m²,what is the amplitude of the magnetic field of this wave? (c = 3.0 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A, ε₀ = 8.85 × 10^-12 C²/N ∙ m²)