0x3XHwmA5XFQ_1210016804_jwk572

# 0x3XHwmA5XFQ_1210016804_jwk572 - homework 11 – KIM JI –...

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Unformatted text preview: homework 11 – KIM, JI – Due: Apr 6 2008, 4:00 am 1 Question 1, chap -1, sect -1. part 1 of 1 10 points The electric field between the plates of an air capacitor of plate area 0 . 45 m 2 is changing at a rate of 42900 V / m / s. The permitivity of free space is 8 . 85419 × 10 − 12 C 2 / N / m 2 . What is Maxwell’s displacement current? Correct answer: 1 . 7093 × 10 − 7 A (tolerance ± 1 %). Explanation: Let : ǫ = 8 . 85419 × 10 − 12 C 2 / N / m 2 , A = 0 . 45 m 2 , and d E dt = 42900 V / m / s , where A is the area and d E dt is the changing rate of the electric field. The displacement current is I D = ǫ A d E dt = ( 8 . 85419 × 10 − 12 C 2 / N / m 2 ) × ( . 45 m 2 ) (42900 V / m / s) = 1 . 7093 × 10 − 7 A . Question 2, chap 33, sect 4. part 1 of 1 10 points What is the fundamental source of electro- magnetic radiation? 1. none of the above 2. voltage 3. charge 4. current 5. an accelerating charges correct Explanation: The fundamental source of electromagnetic radiation is oscillating electric charges, which emit oscillating electric and magnetic fields. Question 3, chap 33, sect 3. part 1 of 1 10 points What is the property of the speed of light in vacuum according to Maxwell’s eqaution? 1. It is greater for visible light than for radio waves. 2. It is a function of the size of the source. 3. It is a function of the distance from the source. 4. It is greater for radio waves than for visi- ble light. 5. It is independent of frequency. correct Explanation: Application of Faraday’s Law and the Ampere-Maxwell equation to EM radiation results in the prediction that the speed of light is c = 1 √ μ ǫ , independent of frequency. Question 4, chap 33, sect 3. part 1 of 1 10 points Gamma-ray bursters are objects in the uni- verse that emit pulses of gamma rays with high energies. The frequency of the most en- ergetic bursts has been measured at around 3 . × 10 21 Hz. The speed of light is 3 × 10 8 m / s. What is the wavelength of these gamma rays? Correct answer: 1 × 10 − 13 m (tolerance ± 1 %). Explanation: Let : f = 3 . × 10 21 Hz and c = 3 . 00 × 10 8 m / s . The speed is c = fλ homework 11 – KIM, JI – Due: Apr 6 2008, 4:00 am 2 λ = c f = 3 × 10 8 m / s 3 × 10 21 Hz = 1 × 10 − 13 m . Question 5, chap 33, sect 3. part 1 of 2 10 points Consider 3 polarizers #1, #2, and #3 or- dered sequentially. The incident light is un- polarized with intensity I . The intensities after the light passes through the subsequent polarizers are labeled as I 1 , I 2 , and I 3 , respec- tively (see the sketch). I I 1 I 2 I 3 #1 #2 #3 Polarizers #1 and #3 are “crossed” such that their transmission axes are perpendic- ular to each other. Polarizer #2 is placed between the polarizers #1 and #3 with its transmission axis at 60 ◦ with respect to the transmission axis of the polarizer #1 (see the sketch)....
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0x3XHwmA5XFQ_1210016804_jwk572 - homework 11 – KIM JI –...

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