HW28Sol - Platt, David – Homework 28 – Due: Nov 14...

This preview shows pages 1–2. Sign up to view the full content.

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Platt, David – Homework 28 – Due: Nov 14 2005, 4:00 am – Inst: Ken Shih 1 This print-out should have 8 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points In 1965 Penzias and Wilson discovered the cosmic microwave radiation left over from the Big Bang expansion of the universe. The energy density of this radiation is 9 . 44 × 10- 14 J / m 3 . The speed of light 2 . 99792 × 10 8 m / s and the permeability of free space is 4 π × 10- 7 N / A 2 . Determine the corresponding electric field amplitude. Correct answer: 0 . 146025 V / m. Explanation: Let : μ o = 4 π × 10- 7 N / A 2 , c = 2 . 99792 × 10 8 m / s , and u = 9 . 44 × 10- 14 J / m 3 . The average poynting vector is given by h S i = E 2 2 μ o c . (1) From this expression we can solve for E in terms of the energy density u knowing that u = h S i c and from this we get the electric field as E = p 2 μ o c 2 u (2) = q 2(4 π × 10- 7 N / A 2 ) × q (2 . 99792 × 10 8 m / s) 2 × q (9 . 44 × 10- 14 J / m 3 ) = . 146025 V / m ....
View Full Document

This note was uploaded on 07/26/2009 for the course PHY 303L taught by Professor Turner during the Fall '08 term at University of Texas.

Page1 / 3

HW28Sol - Platt, David – Homework 28 – Due: Nov 14...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online