AST 101 Exam 2

Chapter 4

Electromagnetic Radiation

-transmission of energy through space varying fields of electricity and magnetism

means light

-if you have electricity/magnetism you can make the other. you need both! equal but different

Speed of light

300,000 kilometers per second

-fast enough to circle the earth 7.5 times per second

Light

takes 8 minutes for the suns ___ to reach earth

waves

light travels in ____

Diffraction

the bending of a wave around an obstacle

ex: a break water that stops waves

Interference

the sum of two waves, could be longer or smaller than the original two waves when they combine

Vibration

how do sound waves work

Quiet

space is very ____

Electromagnetic fields

How do light waves travel with no air

Charged particles/photons

what makes up light waves

Photon

can be positive or negative, carries energy depending on its frequency or wavelength

Visible Spectrum

the colors we see are the ___

Wavelength

color is determined by its ___

it is measured in nanometers

the spot on a wave to the spot on another

wavelength is determined by

Frequency

the number of wave crests that pass a given point in 1 second

measured in hertz

long wavelength=low

short wavelength=high

Prism

demonstrates that white light is a mixture of wavelengths by its creation of a spectrum

a raindrop is an example

temperatures

colors have different ___, short wavelengths have higher energy and higher ____

Electromagnetic spectrum

composed of radio waves, microwaves infrared, visible light, ultraviolet, x rays, and gamma ray (listed in order from longest/lower energy to shortest/higher energy)

long

these wavelengths are more than 10³ km

short

these wavelengths are less than 10^-18 m

rainbow

the beginning (red) of it has the lowest energy and longest wavelengths and the end (purple) has the shortest wavelengths and most energy

wavelength

each photons energy is based on its ___

Spectroscope

splits light into component colors

Emission Lines

single frequencies emitted by particular atoms

can be used to identify elements

Absorption Spectrum

if a continuous spectrum passes through a cool gas, atoms of the gas will absorb the same frequencies they emit

Kirchoff’s Laws

-luminous solid, liquid, or dense gas produces continuous spectrum (aka rainbow)

-low density hot gas produces emission spectrum

-continuous spectrum incident on cool, thin gas produces absorption spectrum (laws 1+2 combined)

Atmospheric Windows

visible, most radio waves, and some infrared go through __

Opague

Totally blocked

Window

Open

Doppler Effect

shifts an objects entire spectrum either towards the red or towards the blue

Celestial objects

• astronomers collect radiation emitted from distant objects

• extremely faint objects make collection diffcult

specialized instruments

modern astronomers used mirror telescope and observations rarely at the eyepiece, at a computer terminal instead

telescope fundamentals

• light is collected proportional to collector area

• mirror or lense

• telescope “funnels” light for a brighter image

• small changed in radius give large change in number of photons caught

refraction

• light moving at an angle from one material to another will bend

when does refraction occur?

When the speed of light is different materials

What do you call a telescope that employ lenses to collect and focus light called?

refractors

What comply refraction to bend light?

lenses

Why will lenses have many disadvantages in a larger telescope?

• a large base will sag in the center since it can only be supported by the edges

• both sides of the lenses needs to be perfect

• chromatic aberration causes images to have colored fringes

• many lenses material absorbs short-wavelength light

What are the advantages to having mirrors for telescopes?

• it is cheaper

• wont sag in the middle

• mirrors only have to be perfect on one side

• no chromatic aberration

What do we use for modern day telescopes?

mirrors

Where is the Keck telescopes located?

Mauna kea in Hawaii

resolving power

a telescopes ability to discern details

For a given wavelength resolution is _________ for a larger telescope

increased

interferometer

combines observations from two or more widely-spread telescope'; resolution is now the same as 1 telescope equal in size to the diameter of all the telescopes

image acquisition

charge coupled devices (ccds) are electronic devices can be quickly read out and reset

Many astronomical objects radiate in ___________ other than visible

wavelengths

______ gas clouds radiate in the radio

cold

_____ clouds radiate in the infraed

dust

______ around block holes emits x-rays

hot glasses

What are technically used to depict wavelengths distributions in non-visible observations?

false color images

Ground base advantages

• larger collecting power

• equipment easily fixed

• cheaper

space based advantages

• no atmospheric blurring

• no atmospheric absorption

• no weather, humidity, and haze

• no light pollution

What telescopes and their equipment require observations?

immesense

What are the largest telescope in the US?

twin 1-meter Keck telescopes

what does VLT mean?

Very large telescope

What is in the way when observing from the ground?

atmosphere

How are temperature and density different?

Pockets of air shift the image of the star

scintillation

the twinkling of stars in the sky caused by moving atmospherics irregulations

How can distortions be improved?

adaptive optics

Adaptive optics

employs a powerful laser and correcting mirrors

Earth

huge, rocky, sphere spinning in space and moving around the sun

What prottects earth’s surface

a blankets of air and a magnetic field

density

is a measure of how much material (mass) is packed into a given volume

What is Earths density?

5.5 g/cm(3)

What is Earths core probably made of?

iron

seismic wave

move through earth at speeds dependent on the properties of the material they go through

______ determined by timing the arrival of the waves at points on the earth’s surface

speed

What is generated of the earth’s interior along the path of the wave?

seismic picture

What the the two types of seismic waves?

S and P

S waves

move up and down; only travel through solids

P waves

compress material; travels through liquid or solid

What waves are NOT on the opposite side of the earth from the earthquater

S waves

Is Earths core liquid?

yes

How was earth formed?

A big cloud of dust, moving/sticking, it becomes more active, the collisions generated heat, enough to melt/ make them stick, gravity pulled to the center

Earth is layered with ______ materials in the center and the least _______ at the surface.

densest/dense

What is the tstimated temp of the earth’s core?

650 k

What occurs in the mix of materials of earth

radiocative deccay

How old is the earth?

about 4 ½ billion years (not even close to my fav number)

What helped determine the earths age?

radioactivity decay

Heat generated by radioactive decay in the earth creation ________/

convection

______ causes plate tectonics

convection

plate tectonics

the surface of earth is broken into plates that all move and change

What allows heat to escape from the interior of earth?

convection

magnetic field

the earth is generated by currents flowing in its molten iron core

Currents are believed to be caused by ________ and _________

rotational motion and convention

magnetosphere

region where the earth’s magnetic field effects particle motion

van Allen radiation belt

two doughnut shaped rings that encircle the earth where chapped particles trapped

as the charged solar particles stream past earth, they generated _______ in the upper atmosphere.

electrical currents

What causes aurora?

electrical currents and excite molecules

The earth’s atmosphere is primarily

nitrogen and oxygen

The oxygen in the atmosphere provides a shield against what?

solar uv radiation

o2 provides some sheliding but _____ or _______ provides most of it

03 pr ozone

earths atmosphere

• release of gas by volcanism or asteroid impacts

• from materials brought to earth by comet impacts

• early atmosphere contained much more methane and ammonia

• solar uv broke those down and made carbon nitrogen and oxygen behind while the hydrogen escaped into space

• ancient bacteria furthered increases the levels of atmosphereic oxygen through photosynthesis