Modern Physics Exam 1

Interferometer

Measures the phase difference between two light waves

Invented by Michelson

Einstein postulate 1 (principle of relativity)

The laws of physics are the same in all internal systems

Einstein postulate (speed of light one)

Observers in all inertial systems measure the same value for the speed of light in a vacuum

Proper time

The time interval between two events occurring at the same position in a system as measure by a clock at rest in the system

Always the shortest time interval

Time dilation

An inertial observer determines that all clocks in motion relative to themselves ran slower than the observers own clock

We say that moving clocks run slower

Proper length

The length of an object measured by an observer at rest

Space contraction

The length of an object measured by on observer at rest will always be shorted when measured by the observer in a system moving in a direction along the meter stick

The length will be shorter only in the direction of relative motion

Each observer will say that the other moving stick is shorter

There is no length contraction perpendicular to the relative motion

Invariant

Quantity that has the same value in all inertial frames

Ex: speed of light

Doppler effect

It causes an increased frequency of sound as a source such as a train approaches and decreases in frequency as the source recedes

Redshift

Change in frequency of light being emitted by an object moving at high speeds relative to us

For lower frequency’s

Blueshift for higher frequency

Binding energy

For a molecule it is the amount of energy required to separate the atoms

It also refers to the difference between the rest energy of individual particles and the rest energy of combined, bound system