PHYSICS 222 FINAL EXAM May 10 2010 NAME PRINT CLEARLY 10 1 Which of the following statements is true if the intensity of a light beam is increased while its frequency is kept the same a The photons gain higher speeds b the energy of the photons is increased c the number of photons per unit time is increased d the wavelength of the light is increased VJ 4 A t p v 10 2 If the proper distance to a star is 5 0 light years what is the distance as measured in a spaceship going to the star at 0 8 c a 6 3 ly b 5 Oly c 4 Oly d 3 OIy t7 10 3 The relativistic mass of a particle is double its rest mass at speed a 0 71c b 0 82c c 0 87c d 1 4c a 4n rz 47 O 1 wi 10 4 A light emitting diode emits one microwatt of 640 nm photons How many photons are emitted each second a 3 2 x 1012 b 2 5 x 1020 c 9 7 x 1020 d 2 0 x h C3X s A zx1o zzz x o 1Y1 2 10 5 The Bohr radius of the hydrogen atom is 0 529 x m The radius of the n 10 10 10 10 a 0 529 x 10 m b 1 06 x m c 2 12 x d 0 265 x i0 m 2 state is r 0 10 6 In the hydrogen atom if the principal quantum number n 4 how many possible values can the angular momentum quantum number I have a 3 b 4 c 8 d 9 ivl 1 1 2 i F t2 1 4 if BLACKBODY RADIATION GOOD ABSORBER is GOOD EMITTER GOOD EMITTER is GOOD ABSORBER PROOF CONSIDER TWO OPAQUE QBJECTS IN THERMAL EQUILIBRIUM A 1 is Emittance of object 1 W 2 is Emittance of object 2 W 1 is Area of object 1 A 2 is Area of object 2 A I is the Intensity of radiation in the region a absorptance r reflectance fraction of radiation absorbed fraction of radiation reflected Consider time interval At Object 1 Total energy radiated 1A W 1 At Total energy absorbed 1 At 1IA a Thermal equilibrium dictates Total energy radiated Total energy absorbed Therefore 1A W 1 At IA 1 a A t Or 1 W 1 a Do same calculation for object 2 2 W 1 2 a Divide first by second to get 2 W 1 a a I 1 a a or w 1 w 2 1 a 7 a or for many objects CD CD CD C CD CD C JD I IC IC rd H H C Cb CD CD CD H II 25 8 Find the wave function and evaluate all constants for an electron trapped in an infinite square well of width L Start with the time independent Schroedinger equation and show each step clearly BE NEAT Vq s tiL cpg1 f 4 tA V 4 441 e C tx s p L A I A J j Cf I frjfr1 4 2 12 A r vi e 20 9 A spherical blackbody with radius of 0 05 m is held at a constant temperature What is the temperature if the power radiated by the body is 1000 J s L e I T 5 Yf4 Ra whose half life is 1620 years 20 10 What is the activity of one gram of 226 cft AW Z Xtc9Ac zoy 4 2 1cy w 2 c 1 X1c s c 3 z k t
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