Amplitude of Magnetic Field - Vibrations and Waves - Past Exam, Exams of Physics

Download Amplitude of Magnetic Field - Vibrations and Waves - Past Exam and more Exams Physics in PDF only on Docsity! Physics 340 Fall 2003 EXAM 2 Each Problem is worth 14 points. 1. A dish antenna with a diameter of 20 m completely absorbs a radio wave which strikes it at normal incidence. The radio wave is a sinusoidal plane wave with electric field of magnitude 0 0.4 / .E V mµ= a. What is the amplitude of the magnetic field of this wave? b. What is the intensity of the radio wave? c. How much energy is absorbed by the antenna in 10 seconds? 2. A transverse traveling wave propagates on a string according to the expression ( , ) (0.35 )sin(10 3 /4)y x t m t xπ π π= − + a. What is the velocity of the wave? (Give speed and direction) b. What are the wavelength and frequency? c. What is the maximum magnitude of the transverse velocity of the string? 3. The sound level at a distance of 3 m from a source is 120 dB. At what distance will the sound level be 10 dB? 4. A right circularly polarized EM wave: 0 0ˆ ˆ( , ) cos( 4) sin( 4)RE z t E kz wt i E kz wt jπ π= − + + − + r overlaps with a left circularly polarized EM wave: 0 0 ˆ ˆ( , ) cos( 4) sin( 4)LE z t E kz wt i E kz wt jπ π= − − − − − r Write the equation for the E field of the resulting wave. What are the amplitude and polarization? 5. A thin tungsten filament of length 1 m radiates EM waves in the radial direction with a total power of 60 W. A perfectly absorbing surface in the form of a hollow cylinder of radius 5cm and length 1 m is placed concentrically with the filament. Calculate the total force on the cylinder from radiation pressure.