Exam 4

1. Exam 4 • We’ll grade it tomorrow afternoon • The problem where you had to had to find n for a hydrogen atom after absorbing a photon . . . Reduce points possible by 9 points, grade out of 3 points.

2. Final Exam All Finals week in the testing center Same format as midterms but no free response - one page of notes - bring a calculator, scratch paper, pencils, erasers

3. Final Exam - 16 multiple choice • 2 problems from each unit like problems on midterms • If I asked a question about pressure change in isothermal, be prepared to do isovolumetric, etc. • If I asked a question about a lens, I might ask a similar one about a mirror, etc. • May be similar to a free response question • 2 problems from each midterm with different numbers

4. Other Announcements • SPS Finals Review • 6-7 in the underground lab • Go to the bottom floor of ESC, middle of hallway running along north of building • Door to the right of a small staircase going up • Open door, go all the way down the stairs • Food at 5 • Course Evaluations • extra credit 20/1 point quiz

5. Rate the Tutors If you used the physics tutorial lab this semester, we invite you to rate the tutors you received help from. Rating form and photos of tutors: http://gardner.byu.edu/tas/tutorrating.php

6. Requested Review • Energy of photon vs wavelength • Energy of atom with a given n

11. Unit 2 Review Ideal Gas—PV=nRT—Watch units W work done by gas vs. on gas Adiabatic, constant V, T and P Thermal equilibrium—Entropy

12. Unit 2 Review Heat --Internal energy – degrees of freedom 1st and 2nd laws of thermodynamics Temperature change: Q=mcT Phase change: Q=mL Radiation, convection, conduction

13. In an ideal gas, if you double the volume of the container, while keeping the temperature and the number of molecules the same, the pressure in the gas • Decreases • Stays the same • Increases

14. Suppose we have two jars of gas, one of helium and one of oxygen. If both jars have the same volume, and the two gases are at the same pressure and temperature, which jar contains the greatest number of molecules? • Jar of helium • Jar of oxygen • Both jars contain the same number. Consider both gases to obey the ideal gas law. Also note that the mass of an oxygen atom is greater than the mass of a helium atom.

15. Cwater=4186 J/kg oCCgold=129 J/kg oCWhich heats up faster using the same heat source? • 1 kg water • 1 kg gold • They both heat up at the same rate. Q is energy transferred

16. Put 100g Al at 100o C into 500g water at 20o C. What is the final T?cAl=900 J/kg oC cH2O=4186 J/kg oCWhat will the final T be? • 100o • 97o • 20o • 23o • 60o

17. The first law of thermodynamics ∆Eint = Q + W Change of internal energy = heat put into system + work done on system The internal energy of an ideal gas depends only on the temperature of the gas.

18. True or False: Given two different objects, the one with the higher temperature contains more heat. (a) T (b) F

19. P V The path shown below is adiabatic (Q = 0). The change in internal energy of the gas is • Positive • Negative • zero

20. P V In the path shown, the change in internal energy of the gas is • Negative • Positive • Zero

21. P V In the path shown below, the gas returns to its original state. The net change in internal energy is • Positive • negative • zero

22. P In the path shown below, the heat Q put into the gas is (a) negative. (b) zero. (c) positive. V

23. P V In the path shown below, the gas returns to its original state. The heat put into the gas is • Positive • negative • zero

24. One of the P-V curves below is for an isothermal process. The other is for an adiabatic process. Which is adiabatic?

25. Two gases in separate containers have equal volumes, equal numbers of molecules, and the same internal energy Eint. However, one gas is monatomic and the other is diatomic. The pressure of the diatomic gas is • Less than that of the monatomic gas. • The same of that of the monatomic gas. • Greater than that of the monatomic gas.

26. The second law of thermodynamics says for a heat engine • You can’t get more work energy out than you consume in heat • You can’t get out all of the heat energy as work • You will get out more work energy than you consume in heat

27. Did you know, for example, that the two greatest intellectual achievements of the last century, the general theory of relativity and quantum mechanics, are in some points in conflict with each other. They cannot both be right in every detail. These are not my words, but the words of Stephen Hawking, the great British physicist. Yet, scientists rely on both of these theories every day to advance scientific knowledge, knowing that some day the differences will be understood, reconciled, and corrected.

28. So it is with the gospel and our testimonies, yours and mine. This is not to suggest that the gospel is imperfect, but our understanding of it sometimes is. Like the scientist that uses relativity and quantum mechanics, we do not discard the gospel or our testimony because not every piece fits today. Richard G. Hinckley Prophetic Priorities BYU Devotional, May 15, 2007

29. Unit 3 Review • Ray approximation • Reflection • Refraction-Snell’s Law

30. Unit 3 Review • Mirrors-equations and drawing principle rays • Lenses-equations and drawing principle rays

31. Unit 3 Review • Real and virtual images • Magnification

32. Unit 3 Review • Camera • Glasses • Magnifying glass

33. Unit 3 Review • Microscope • Telescope

34. Unit 3 Review • Double and Single slit interference • Diffraction Grating

35. Unit 3 Review • Thin film interference • Telescope (eye, radar dish, etc.) resolution

36. An object is placed in front of a concave mirror. Depending on the position of the object, the image formed may occur • Behind the mirror and be real • In front of the mirror and be virtual. • In front of the mirror and be upright • None of the above

37. Which of the following best describes the image for a thin diverging lens that forms whenever the magnitude of the object distance is less than that of the lens' focal length? • Real and upright • Real and inverted • Virtual and upright • Virtual and inverted

38. You are designing eyeglasses for someone whose near point is 60 cm. What focal length lens should you prescribe so that an object can be clearly seen when placed at 25 cm in front of the eye? • -15 cm • -18 cm • 18 cm • 43 cm • 60 cm

39. Group question: a flat glass microscope slide (n=1.5) with parallel sides in air is illuminated with green light (λ=520 nm). Light reflects off both surfaces. What do you see in top view (what is the combined light reflected off the slide)? • All dark • All bright • Dark and bright fringes • Not enough information is given

40. Discussion question: An oil film on water reflects different colors more or less brightly owing to interference, depending on the film thickness. All the colors reflect brightly where the film is thinnest. (thin compared to visible wavelengths, approximately zero but enough to have a reflected ray off the oil and the water), From this information, we can tell that the index of refraction of the oil is • Less than that of water. • The same as that of water. • Greater than that of water.

41. Discussion question: An interference pattern is formed on a screen by shining a planar wave on a double-slit arrangement (left). If we cover one slit with a glass plate (right), the phases of the two emerging waves will be different because the wavelength is shorter in glass than in air. If the phase difference is 180°, how is the interference pattern, shown left, altered? • The pattern vanishes • The bright spots lie closer together. • The bright spots are farther apart. • There are no changes. • Bright and dark spots are interchanged

42. Unit 4 Review Relativity Postulates of Special Relativity Time Dilation Length Contraction

43. Unit 4 Review Relativity Lorentz Transformations Adding velocities Relativistic energy and momentum

44. After your friend drives past you in a car at a speed of 0.6 c, they turn on their headlights, and in their reference frame they measure the light traveling away from them at 2.9979x108 m/s. How fast will YOU measure the light traveling? • 2.9979x108 m/s • Less than 2.9979x108m/s • More than 2.9979x108m/s

45. Your friend waves at you while they drive past you in a car. Who measures the proper time for how long they waved at you? (a) You (b) Your friend (c) None of the above

46. Your friend waves at you while they drive past you in a car. Who measures the longer time for how long they waved at you? (a) You (b) Your friend

47. Your friend waves at you while they drive past you in a car. Who measures the proper length of their car? (a) You (b) Your friend (c) None of the above

48. Your friend drives past you in a car traveling at a velocity of 0.8 c. Your enemy travels past you in the opposite direction at a speed of 0.7 c. What velocity will your friend measure your enemy to be moving at? • 0.1 c • c • 1.5 c • None of the above

49. Your friend drives past you in a car traveling at a velocity u. The car has a mass m. What is the momentum of the car? • mv • mc • γmc • γmv • None of the above

50. Your friend drives past you in a car traveling at a velocity u. The car has a mass m. What is the kinetic energy of the car? • (1/2) mv2 • mc2 • γmc2 • None of the above