PHYS 1, Homework 7 Due Friday, March 9 in class Instructions: Please complete th

Question

PHYS 1, Homework 7 Due Friday, March 9 in class Instructions: Please complete the homework problems on sheets of loose-leaf paper, stapled together. Label each problem clearly, write neatly, and give yourself plenty of space to answer questions. For any calculations, show your work. The homework grader may deduct points for neatness at his discretion. Please hand in the assignment during lecture on the due date above. Late homework is not accepted, so if you can't make it to lecture on the given due date, please make arrangements with me well in advance of the homework deadline. Problem 1: When an iron rod is heated to hundreds of degrees Celsius, it begins to glow red. Why does it do this? (Hint: think about Feynman's "jiggling" atoms, atomic structure, and the nature of light) Problem 2: Suppose that two positive charges (i and q2) are traveling parallel to one another at speed v, separated by a distance d, as shown in the diagram below: (a) What is the magnitude of the (repulsive) electric force? Express your answer algebraically. (b) In addition to repelling one another electrically, the two charges attract one another magnetically. The formula for the magnetic force of attraction here is Fmagnetic U2

Explanation / Answer

When iron is heated the atoms kinetic energy increases and some electrons after gaining this energy move to higher energy excited states. when the electron comes back to it's original lower energy state it emits the extra energy in form of photons of light. These photons have a particular frequency (or wavelength) which depends upon the energy difference between the levels. So when electrons jump back to the original state it emits a photon of red color in case of iron because in iron the energy gap corresponds to the wavelength of red color.

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