Astronomy Chapter 2

Front 1

What is the wave nature of light?

Back 1

a way to transfer energy from place without the physical movement of material from one location to another

Front 2

Wave characteristics:

Distance between successive wave peaks

Back 2

Wavelength

Front 3

Wave charactistics:

Time between passing wave peaks

Back 3

Period

Front 4

Wave characteristics:

Number of wave peaks passing per unit time (1/Period)

Back 4

frequency

Front 5

wave characteristics:

wavelength x frequency

Back 5

Wave speed

Front 6

what is the speed of light?

Back 6

3e8 m/s

Front 7

Sound waves travel by vibrating the molecules between the source and listener. Is this how light travels?

Back 7

Light does not require a medium in which to travel… Light can travel thru a vacuum.

Front 8

The changing position of a charged particle creates

Back 8

“waves” in the field lines.

Front 9

Moving charges also produce

Back 9

Magnetic fields (accelerating charges).

Front 10

magnetic fields force charged particles

Back 10

to move (to accelerate)

Front 11

** WHAT CAUSES LIGHT? **

Back 11

E&M Waves produce LIGHT!

Front 12

If Electromagnetic waves creat light, what creates electricmagnetic waves?

Back 12

Accelerating charges (electrons, protons)

Front 13

The waves of electric field and that of the magnetic field propogate...

Back 13

at right angles to one another.

Front 14

While the electric field and magnetic field are at right angles to one another. What direction is the wave's motion?

Back 14

90 degrees from both the electric field and 90 degrees from the magnetic field.

Front 15

What is the range of the EM spectrum, from least to most energy?

Back 15

Radio, Infared, Visible (Red to Violet), Ultraviolet, X-ray, Gamma

Front 16

As energy increases, what happens to the wavelength? frequency?

Back 16

wavelength decreases as energy increases. Frequency increases as energy increases.

Front 17

Where would microwaves fall on the EM spectrum?

Back 17

Between Radio waves and infared.

Front 18

Why are optical telescopes built on hill tops or at high elevation?

Back 18

Because the ATMOSPHERE ABSORBS some of the light coming from space. Minimizing the atmospheric content between the telescope and space increases the amount of light it will recieve.

Front 19

What makes objects emit EM radiation?

Back 19

when charged particles change their rate of motion, they emit EM radiation.

Front 20

measures the amount of motion of the particles

Back 20

temperature

Front 21

In other words, the hotter the object...

Back 21

the higher its temperature and the MORE movement it's particles have.

Front 22

All solid/dense objects emit radiation having a characteristic spectrum called

Back 22

blackbody

Front 23

Hotter blackbodies are (color)

Back 23

Bluer and brighter

Front 24

If all bodies emit EM waves, why cant we see one another in a dark room?

Back 24

Because the EM radiation given off by the body is in the IR not in the visible spectrum.

Front 25

Why is the sun yellow?

Back 25

because AT ITS MAXIMUM INTENSITY, it's wavelength is in the yellow visible region.

Front 26

Wien's law states that Hotter bodies radiate more strongly at..

Back 26

SHORTER WAVELENGTHS (BLUER)

Front 27

Mathematically, what is Wien's law?

Back 27

Wavelength= .29 cm/ Temp(K)

Front 28

Why is wien's law so important?

Back 28

Knowing a star's wavelength by simply observing the light it emits, we can determine the star's TEMPERATURE!

Front 29

Stefan's law states that hotter blackbodies are...

Back 29

brighter (at any wavelength).

Front 30

Mathematically, what is stefan's law?

Back 30

F = sigma x T4

F= flux
sigma= constant

Front 31

Experimentally, how is a continuous spectrum produced?

Back 31

By passing white light through a slit and through a prism.

Front 32

Experimentally, how is a emission line spectra created?

Back 32

Passing the light from a heated gas through a slit.

Front 33

What does each unique pattern of lines tell us?

Back 33

the chemical composition of the gas. Each compound produces a unique spectra.

Front 34

Experimentally, how is an absorption line spectrum created?

Back 34

passing hot light through a cooler gas and passing it through a slit.

Front 35

Kirchoff's Laws:

First law: hot, dense gasses or solids produce a

Back 35

Continuous spectrum (light bulb)

Front 36

Kirchoff's Laws:

Second law- hot rarefied gases produce an...

Back 36

emission line spectrum.

Front 37

Kirchoff's Laws:

Third law- Cool gas in front of a hot continuous source produces an

Back 37

absorption line spectrum

Front 38

What are the three subatomic particles that make up an atom?

Back 38

electrons, protons, and neutrons.

Front 39

Atoms are mostly....

Back 39

empty space. the protons and neutrons are squeezed into a tiny space whereas the electrons circle widely around. EMPTY SPACE IN BETWEEN!

Front 40

what makes each atom of a given element unique?

Back 40

The number of protons and ELECTRONS!

Front 41

*** The Bohr Hydrogen model states that...

Back 41

every hydrogen atom has one electron circling a proton.

Front 42

How did Bohr suggest the electron remained in orbit?

Back 42

by the Columb effect (inverse squared law)

Front 43

Bohr suggested that electrons can orbit in particular energy states. How would an electron change energy states?

Back 43

Electrons would go from the energy state to more energetic states by absorbing energy (usually a photon). In order to return to the ground state the electron releases this energy (usually in the form of light).

Front 44

That energy (which is added or released when the electron changes orbit levels) is

Back 44

photons of light

Front 45

Atoms can only absorb or emit photons having energy exactly equal to

Back 45

the energy difference between electron orbits

Front 46

High energy photons correspond to short wavelength light and may boost the electron so much that it is completely ejected from the atom! This process is called?

Back 46

Ionization

Front 47

TO CLARIFY: Every e- “transition” corresponds to

Back 47

a unique wavelength.

Front 48

In modern quantum mechanics:
Electrons are not just particles, but also

Back 48

waves, without exact locations

Front 49

Moving sources, like fire trucks and race cars, change pitch as they go by… This phenomenon is known as?

Back 49

Doppler effect

Front 50

As an object passes you, does the pitch go up or down

Back 50

down

Front 51

Doppler shift: Stars moving toward us appear what color? Those moving away appear what color?

Back 51

Blue (Blue-shifted)

Red (Red-shifted)

Front 52

What can we determine by spectroscopy of the light we observe from stars?

Back 52

Chemical composition (spectral lines)
Temperature (blackbody)
Velocity (doppler)
Rotation rate (doppler)
Pressure (spectral lines)
Magnetic field (Zeeman effect)