Physics Option E Terms And Relativity

Front 1

Arc Second

Back 1

One degree split up into seconds (1/3600 of a degree).

Front 2

Light Year

Back 2

The distance light travels during one year

ly

Front 3

Absolute Luminosity

Back 3

The total power radiated from a star in watts

W

Front 4

Apparent Luminosity/Brightness

Back 4

Power of star light reaching Earth in .

b

Front 5

Absolute Magnitude

Back 5

Apparent Magnitude of a star at a standard distance of 10 parsec.

M

Front 6

Apparent Magnitude

Back 6

How bright a star looks (scale 6 to 1, 1 being the brightest).

m

Front 7

Black Body

Back 7

Hot body who’s emission spectrum depends on its temperature only (stars are considered black bodies because they emit all energy produced).

Front 8

Black Body Radiation

Back 8

Radiation from a theoretical “perfect” emitter.

Front 9

Cepheid Variable Star

Back 9

Stars that varies periodically in size (not mass!!) and hence luminosity (used to determine distances greater than 10 Mpc).

Front 10

Binary Star

Back 10

Two or more stars that orbit around each other.

Front 11

Planetary Order

Back 11

Mercury, Venus, Earth, Mars, Asteroid Belt, Jupiter, Saturn, Neptune, Uranus, Pluto

Front 12

Eclipsing Binaries

Back 12

Two stars that regularly eclipse each one another causing a periodic variation in brightness.

Front 13

Red Giant

Back 13

A large and relative cool star in one of the later stages of its life. The source of its energy is fusion of some other element than hydrogen.

Front 14

Red Super Giant

Back 14

A very large mass and relative cool star in one of the later stages of its life. The source of its energy is fusion of some other element than hydrogen.

Front 15

White Dwarf

Back 15

A small and relative cool star at one of the possible final stages of a star’s life. Fusion is no longer taking place and hence it is cooling down.

Front 16

Parsec

Back 16

1 parsec is the distance which will give a parallax angle of exactly 1 arc second, with 1 AU as the baseline (3.26 light years).

pc

Front 17

Astronomical Unit

Back 17

The radius of Earth’s orbit around the Sun

AU

Front 18

Red Shift

Back 18

Increase in wavelength emitted from galaxies and stars moving away from Earth. This can either be due to the Doppler Effect or expansion of space (which expands the wave).

Front 19

Critical Density

Back 19

The theoretical density of the universe necessary to create a “flat” universe after an infinite amount of time

Front 20

Dark Matter

Back 20

Not seeable matter that must exist to explain the lack of observable gravitational matter that make the stars orbit the galactic centre.

Front 21

MACHOs

Back 21

Black holes, high-mass planets or/and failed stars – all who produce very little or no light (hence not seeable).

Front 22

WIMPs

Back 22

A new type of particle that can prove the existence of dark matter.

Front 23

Newton's First Postulate about the Universe

Back 23

The universe is infinite.

Front 24

Newton's Second Postulate about the Universe

Back 24

Mass is uniformly distributed in space.

Front 25

Obler's Paradox

Back 25

Why is not the sky bright at night if there is a bright star at every point in the sky? (Inverse Square Law)

Front 26

Wein's Displacement Law

Back 26

Wavelength of radiation with maximum intensity (peak wavelength) is inversely proportional to the temperature of the black body.

Front 27

Stefan-Boltzman Law

Back 27

Links the total power output radiated by a black body to its temperature.

Front 28

Frame of Reference

Back 28

Set of rulers from which measurements can be made.

Front 29

Galilean Transformations

Back 29

Relate distance and velocity in one frame of reference to another.

Front 30

Inertial Frame of Reference

Back 30

Frame of reference where the laws of inertia (Newton’s Laws) apply.

Front 31

Proper Time

Back 31

The time measured by an observed who is at the same place as the event.

Front 32

Proper Length

Back 32

The length measured by an observer who is at the same place as the event.

Front 33

Rest Mass

Back 33

The mass of a body measured by an observer who is at rest relative to the body.

Front 34

Relativistic Mass

Back 34

The mass of a body measured by an observer who has a velocity other than zero relative to the body.

Front 35

Rest Mass Energy

Back 35

The energy “locked up” in the mass of the body at rest.

Front 36

Total Energy

Back 36

The sum of a body’s rest mass energy and relativistic kinetic energy.

Front 37

Einstein's First Postulate of Special Relativity

Back 37

The laws of Physics are the same in every inertial frame of reference.

Front 38

Einstein's Second Postulate of Special Relativity

Back 38

Light propagates through empty space with a definite speed c, independent of the speed of the source or observer.