Integrated Concepts. On its highest power setting, a microwave oven increases the temperature of 0.400 kg of spaghetti by 45.0✬ in 120 s.(d) How long will it take to increase the temperature of the 4.00-kg shoulder by 2.00º C, assuming no other heat transfer and given that its specific heat is 3.47 × 10 3 J/kg⋅✬? (a) If the lamp’s 200-W output is focused on a person’s shoulder, over a circular area 25.0 cm in diameter, what is the intensity in W/m 2? (b) What is the peak electric field strength? (c) Find the peak magnetic field strength. Integrated Concepts.Assume the mostly infrared radiation from a heat lamp acts like a continuous wave with wavelength 1.50μm.If 1.50 × 10 9-Hz microwaves are used and a beat frequency of 150 Hz is produced, what is the speed of the vehicle? (Assume the same Doppler-shift formulas are valid with the speed of sound replaced by the speed of light.) Beats are produced by mixing the double Doppler-shifted echo with the original frequency. Integrated Concepts. Police radar determines the speed of motor vehicles using the same Doppler-shift technique employed for ultrasound in medical diagnostics.Integrated Concepts. What capacitance is needed in series with an 800- μH inductor to form a circuit that radiates a wavelength of 196 m?.(a) What is the resonant frequency? (b) What inductance is in series with the capacitor? Integrated Concepts. An LC circuit with a 5.00-pF capacitor oscillates in such a manner as to radiate at a wavelength of 3.30 m.(b) Show that the magnitudes of the electric and magnetic fields are inversely proportional to r. (a) Show that the intensity is inversely proportional to r 2, the distance from the source squared. Suppose a source of electromagnetic waves radiates uniformly in all directions in empty space where there are no absorption or interference effects.\displaystyle\\, where rms means average (actually root mean square, a type of average). In fact, for a continuous sinusoidal electromagnetic wave, the average intensity I ave is given by Thus the energy carried and the intensity I of an electromagnetic wave is proportional to E 2 and B 2. In electromagnetic waves, the amplitude is the maximum field strength of the electric and magnetic fields. This is true for waves on guitar strings, for water waves, and for sound waves, where amplitude is proportional to pressure. Now how would you calculate the intensity of a reflected ray at the point given in the figure, or does it even make sense to talk about the intensity of a single ray optics reflection geometric-optics intensity Share. Clearly, the larger the strength of the electric and magnetic fields, the more work they can do and the greater the energy the electromagnetic wave carries.Ī wave’s energy is proportional to its amplitude squared ( E 2 or B 2). If absorbed, the field strengths are diminished and anything left travels on. Once created, the fields carry energy away from a source. With electromagnetic waves, larger E-fields and B-fields exert larger forces and can do more work.īut there is energy in an electromagnetic wave, whether it is absorbed or not. Energy carried by a wave is proportional to its amplitude squared.
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