24-3 - brown (twb493) – Ch24-h3 – chiu – (56565) 1...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: brown (twb493) – Ch24-h3 – chiu – (56565) 1 This print-out should have 18 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points A particular AM radio station broadcasts at a frequency of 650 kHz. What is the wavelength of this electromagnetic radiation? Remember that c = 3 × 10 8 m / s. Correct answer: 461 . 538 m. Explanation: The wavelength of the radiation is c = λ f ⇒ λ = c f = 3 × 10 8 m / s 650 kHz = 461 . 538 m . 002 (part 2 of 2) 10.0 points How much time is required for the radiation to propagate from the broadcasting antenna to a radio 7 . 5 km away? Correct answer: 2 . 5 × 10- 5 s. Explanation: The radiation propagates at the speed of light, so we have c = distance Δt ⇒ Δ t = distance c = 7 . 5 km 3 × 10 8 m / s = 2 . 5 × 10- 5 s . 003 (part 1 of 2) 10.0 points The wavelength of orange light is about 590 nm. What is the frequency of this ra- diation? Use c = 3 × 10 8 m / s. Correct answer: 5 . 08475 × 10 14 Hz. Explanation: The frequency of the orange light is c = λ f ⇒ f = c λ = 3 × 10 8 m / s 590 nm = 5 . 08475 × 10 14 Hz . 004 (part 2 of 2) 10.0 points What is the period of this radiation? Correct answer: 1 . 96667 × 10- 15 s. Explanation: The period is given by T = 1 f = 1 5 . 08475 × 10 14 Hz = 1 . 96667 × 10- 15 s . 005 (part 1 of 4) 10.0 points A slab (pulse) of electromagnetic radiation that is 18 cm thick is propagating downward (in the − y direction) toward a short horizon- tal copper wire of diameter 1 . 2 mm located at the origin and oriented parallel to the z axis, as shown in the figure below. E E E v x y z Wire The direction of the electric field inside the slab is out of the page (in the + z direction). What is the direction of the magnetic field inside the slab? Choose the unit vector corre- sponding to this direction. 1. ( , 1 , ) 2. ( , , 1 ) brown (twb493) – Ch24-h3 – chiu – (56565) 2 3. (− 1 , , ) correct 4. ( , , − 1 ) 5. ( , − 1 , ) 6. ( 1 , , ) Explanation: Inside the pulse, vector B must be to the left (in the − x direction), because vectorv is in the direction of vector E × vector B . 006 (part 2 of 4) 10.0 points You stand on the x axis at location ( 8 , , ) m , at right angles to the direction of propagation of the pulse. The pulse passes the copper wire at time t 1 = 0, and at a later time t 2 you ob- serve new nonzero electric and magnetic fields at your location. What is t 2 ? Remember that c = 3 × 10 8 m / s. Correct answer: 2 . 66667 × 10- 8 s. Explanation: Some time after the original pulse passes the wire, you see the new pulse, produced by reradiation from the copper wire, with vector E into the page, and vector B up. Since you are 8m away from the wire, the time for the reradiation to reach you is t 2 = d c = 8 m 3 × 10 8 m / s = 2 . 66667 × 10- 8 s ....
View Full Document

This note was uploaded on 12/01/2011 for the course PHY 303L taught by Professor Turner during the Fall '08 term at University of Texas.

Page1 / 7

24-3 - brown (twb493) – Ch24-h3 – chiu – (56565) 1...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online