Midterm 1 Solutions Sp01

# Modern Physics

• Homework Help
• davidvictor
• 4

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

PHY251 Midterm I Exam PHY 251 Midterm I Exam March 7 2001 I. Short Answer Questions (110 points) 1. List the crucial experimental evidence that showed that classical Newtonian mechanics was a low- velocity approximation of relativistic mechanics. Solution: (5 points) Michelson-Morley, who showed that all electromagnetic waves (predicted by Maxwell's equations) propagate with the same speed c in vacuum, regardless of inertial frame of the source or receiver. 2. List three types of experimental evidence that testify to the quantum character of the theory of radiation. Solution: (9 points) Planck's blackbody radiation, photoelectric effect, Compton scattering 3. List two types of experimental evidence that can be understood by assuming that sub-atomic particles like electrons have a wave-character. Solution: (6 points) Electron diffraction and interference, Bragg scattering of electrons (Davisson-Germer), Tunneling, Bohr's explanation of the hydrogen spectrum. 4. Consider a moving clock and a moving meter stick (moving parallel to its long dimension) both speeding at constant v = 0.8 c past a stationary observer (you). a. Calculate the length you will measure the speeding meter stick to have. Solution: (5 points) g = 1/ Ö (1-0.64) = 1/0.6 = 10/6; L ' = L 0 / g = 0.6 m b. Calculate the time that passed on the speeding clock if a clock in your rest frame indicates that 3.0 ns have passed. Solution: (5 points) Moving clock will "tick" slower: t' = gt 0 t 0 = 3.0 ns/ g = 1.8 ns c. Indicate how you would set up the experiment for the measurement in part b) above. Solution: (5 points) Several ways: set up two clocks that are perfectly synchronized, and move them c ×3 ns = 0.30 m apart, along the direction of the speeding clock. Rig a trigger close to each of the observers\'s clocks, so that when the moving clock passes, a nearby camera takes a picture. Comparison of the two pictures will then show the time differences on the

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

This is the end of the preview. Sign up to access the rest of the document.
• Spring '01
• Rijssenbeek

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern