Exam 25: EM Induction and Em Waves

Three ideal polarizers are oriented as follows: The axis of the second polarizer is at an angle of 59.0° relative to the first one. The axis of the third polarizer is at an angle of 31.0° relative to the second one, so the axis of the axis of the third polarizer is perpendicular to the axis of the first one. Unpolarized light of intensity $18.6 \mathrm {~W} / \mathrm { m } ^ { 2 }$ is incident on the first polarizer. (a) What is the intensity of the light after it passes through all three polarizers? (b) What is the intensity of the transmitted light if the second polarizer is removed?

A coil lies flat on a horizontal tabletop in a region where the magnetic field points straight down. The magnetic field disappears suddenly. When viewed from above, what is the direction of the induced current in this coil as the field disappears?

Unpolarized light of intensity I₀ passed through an ideal polarizing sheet with its polarizing axis at the 12 o'clock position and then through a second ideal sheet with its polarizing axis at the 1 o'clock position. What is the intensity of the emerging light in terms of I₀?

A bar magnet is oriented above a copper ring, as shown in the figure. The magnet is dropped and passes completely through the ring. As viewed from above, what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it?

An electromagnetic flowmeter is useful when it is desirable not to interrupt the system in which the fluid is flowing (such as the blood in an artery during heart surgery). Such a device is illustrated in the figure. The conducting fluid moves with speed v in a tube of diameter d. Perpendicular to this tube is a magnetic field B. A voltage V is induced between opposite sides of the tube due to the motion of the conducting fluid in the magnetic field. For a certain case, B = 0.120 T, d = 1.2 cm, and the measured voltage is $V = 2.88 \mathrm { mV }$ Determine the speed of the fluid.

Two identical metal bars are heated up until they are both glowing. One of them is "red hot" and the other is "blue hot." Which one is hotter, the one that glows red or the one that glows blue?

A constant uniform magnetic field of 0.50 T is applied at right angles to the plane of a flat rectangular loop of area 3.0 × $10 ^{- 3}$ $m ^ { 2 }$ . If the area of this loop changes steadily from its original value to a new value of 1.6 × 10^-3 m² in 1.6 s, what is the emf induced in the loop?

How much energy is transported across a 1.00-cm² area per hour by a sinusoidal electromagnetic wave whose electric field has a maximum strength of 30.4 V/m? (ε₀ = 8.85 × 10^-12 C²/N ∙ m², μ₀ = 4π × 10^-7 T ∙ m/A, c = 3.0 × 10⁸ m/s)

As shown in the figure, two parallel wires carry a current I in opposite directions, and this current is decreasing. A rectangular loop is centered between the wires. The direction of the induced current through the resistor R is

The wire in the figure carries a current I that is decreasing with time at a constant rate. The wire and the three loops are all in the same plane. What is true about the currents induced in each of the three loops shown?

An object having a fixed emissivity of 0.725 radiates heat at a rate of 10 W when it is at an absolute temperature T. If its temperature is doubled to 2T, at what rate will it now radiate?

A radio station broadcasts at 80 MHz. How long does it take for this radio signal to travel a distance of $2.0 \times 10^7 \mathrm {~m}$ through space? (c = 3.0 × 10⁸ m/s)

As shown in the figure, a coil of wire is placed in the xy-plane, centered on the z-axis. A solenoid is centered on the z-axis and is carrying a steady dc current. Which one of the following actions will not result induce an emf in the coil?

If you double the frequency of the light in a laser beam, but keep the number of photons per second in the beam fixed, which of the following statements are correct? (There could be more than one correct choice.)

As shown in the figure, a wire and a 10-Ω resistor are used to form a circuit in the shape of a square with dimensions 20 cm by 20 cm. A uniform but non-steady magnetic field is directed into the plane of the circuit. The magnitude of the magnetic field is steadily decreased from 2.70 T to 0.90 T in a time interval of 96 ms. What is the induced current in the circuit, and what is its direction through the resistor?

A vertically polarized beam of light of intensity 100 W/m² passes through two ideal polarizers. The transmission axis of the first polarizer makes an angle of 20.0° with the vertical, and the transmission axis of the second one makes an angle of 40.0° with the vertical. What is the intensity of the light after it has passes through both polarizers?

A beam of light is polarized in a vertical plane and has an intensity I₀. The beam passes through an ideal polarizer and then through an ideal analyzer whose axis is set horizontally. If the axis of the polarizer is set at 60° with the vertical, what is the ratio of the intensity of the final beam to I₀?

A flat coil having 40 turns, each one of cross-sectional area 12.0 cm², is oriented with its plane perpendicular to a uniform magnetic field. The field varies steadily from 0.00 T to 1.20 T in 20.0 ms. What emf is induced in the coil during this time?

Which of the following statements about electromagnetic waves in free space are true? (There could be more than one correct choice.)

As shown in the figure, a battery supplies a steady current to the solenoid on the left. The two solenoids are moving toward each other with speeds v. The direction of the induced current through the resistor R is