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## Physics 252 Midterm Review Sheet

The midterm will have five problems. A good way to prepare is to review the web notes, and be sure you know how to do all the homework assignments.

### You need to know by heart the following:

Time dilation and length contraction formulas.
Lorentz transformations: x, t to x', t' and E, p to E', p'.

Addition of velocities formula.
Mass increase. Energy-momentum relationship.
Energy-mass equivalence.
Doppler shift for light.

Speed of light = 3 x 108 meters per second

Avogadro's Number NA = 6 x 1023 particles/mole

(Remember, a mole is the molecular weight in grams, not kilograms)

Boltzmann's constant = 1.4 x 10-23 Joules/K

Planck's constant h = 6.6 x 10-34 Joule-sec

Electron mass = 9 x 10-31 kilograms

Electron charge = 1.6 x 10-19 coulombs

### Topics to Review (besides Relativity)

Kinetic Theory of gases:

How to derive pressure from simple molecular picture.

There is on average an energy ½kT in each degree of freedom.

The probability of a molecule having energy E is proportional to e-E/kT.

How this relates to Maxwell's distribution.

Simple ideas about light interacting with matter: transparency, reflection, etc.

Stefan's Law. (You don't need to memorize the constant)

Wien's displacement law. (Similarly)

Know the approximate wavelengths and frequencies for visible light.

State what was the "ultraviolet catastrophe", and how Planck resolved it.

Be able to sketch the black body curve and explain the low and high frequency parts.

The Photoelectric Effect:

Be able to describe Lenard's experiment (or a more recent version - just a standard photoelectric effect experiment, in other words), what is expected classically on changing light intensity and color, what is actually observed, and how this can be used to find Planck's constant.
How were the photoemitted particles identified?

Rays and Particles:

Be able to describe Thomson's measurement of e/m for cathode rays.

How x-rays were discovered, how their properties were found, how an x-ray tube can be used to find Planck's constant.

How radioactivity was discovered, approximately how much energy radium puts out, what are the alpha, beta and gamma rays, and how do we know?