Midterm 2

The Difference between reflecting & Refracting light

The Difference between reflecting & Refracting light

reflecting occurs when light simply bounces back towards the source. Refracting is the redirection of light.

Describe the two main aspects of a telescope

To gather as much light as possible in as much detail as possible.

Define Focal length

The Focal Length is the distance between the mirror and the focal point. Note: Diff. lenses will have diff. focal lengths.

Define Focal Point

where all light rays converge

Two reasons why bigger telescopes are better

Better at gathering light and more details when taking images.

What is angular resoloution?

Angular resolution is the smallest angle between close objects that can be seen Cleary to be seperate

What is the angular resolution Formula

Sinθ=122λ/D ; D= Telescope diameter , λ= wavelength

Why are large telescopes not refractors?

Refractors are not practical, they are to heavy and the tubes would be very long

What are the two main ways our atmosphere affects light

Does not let certain light through our atmosphere. When the sunlight passes through the atmosphere, shorter (blue) wavelengths are less scattered then other wavelengths

The three diff. types of telescopes.

Cassegrain, Newtonian, Nasmyth/Coude

Cassegrain Telescope

Two mirrors. Primary mirror reflects light towards the secondary mirror. The secondary mirror reflects light through a hole in the primary mirror.

Newtonian Telescope

Two mirrors. Primary reflects light towards the Secondary mirror. The Secondary mirror reflects light to the side of the telescope.

Nasmyth/Coude Telescope

Three mirrors, Primary light reflects light towards the secondary mirror. Secondary mirror reflects light towards the third mirror. Third mirror reflects light to the side of the mirror. Reflects light to the side lower than the Newtonian model

The difference between ground telescopes & Space telescopes

Ground telescopes are subjected to the twinkling of stars so images aren't always clear. Can only observe the light that passes through the atmosphere, such as Radio, Visible, some IR, & some UV. Easier & cheaper maintenance as well as a longer lifetime. Space telescopes are expensive & harder to maintain, but can observe all forms of light.

Photosphere

The sphere of light, deepest layer of the Sun’s atmosphere Visible light comes from this layer 400 km thick Not transparent, gives Sun an apparent surface Granules are located here Hot gas comes up & cools off, then goes down bubbles

Chromosphere

Sphere of color 2,000 km thick Generally transparent Gives off reddish color due to hydrogen spectral lines Spicules are located here Look like blades of fiery grass

Corona

Several million km above chromosphere Heated by the Sun’s magnetic field 10,000 K in temperature Not dense, 10 trillion times less dense than the sea level atmosphere on Earth Gasses from this place gets blown out & creates solar winds

Sunspots

dark spots seen on the Sun because they are cooler & dimmer relative to the rest of the Sun

Plages

bright spots in the chromosphere that appear white because they have a higher temperature & density than surrounding areas

Prominences

loops of plasma that erupt from the photosphere into corona

Flares

giant eruptions that get pinched off or thrown from the Sun

Coronal Mass Ejections (CME)

type of solar wind where material gets ejected from corona

How do we know the composition of the sun?

by looking at the light spectrum since different elements light spectrum look different. Cecila payne-Gaposchkin in 1925 suggested that the sun was composed of mainly hydrogen and helium

Describe the three steps to the PP-chain

Step1. 1H + 1H -> 2H+ e+ + v

Step 2. 1H + 2H -> 3He + V

Step 3. 3He + 3He -> 4He +1H+1H

Sun's Core

where p-p chain happens

Radiative Zone

transfer energy from inside to outside by radiation (photons carry E and hit particle to transfer energy)

Convective Zone

giant blobs of gas transfer heat up, cool, then go back down

Properties of Neutrinos

Neutrinos are the most abundant particles with mass

it passes through everything

10^38 neutrinos produced in sun per second

changes state when moving through space but starts of the same

3 General characteristics of the Solar System

Orderly motion Nearly circular orbits in the same plane all moving counterclockwise Almost all spinning CCW 2 types of planets Terrestrial Jovian Asteroids (rocky) and comets (icy)

Exceptions

Venus spinning upside down Uranus spinning sideways Earth's Moon relatively huge

Formation of the Solar system

Cloud of gas and dust with some rotation Cloud got hit (e.g. by a shockwave) Cloud collapses only itself (into a disk) Proto Sun forms, disk flattens because of angular momentum Sun starts shining, hydrogen fuses into helium, and blows out gases away towards the outer regions of the system. Leftover debris clumps together into larger pieces which eventually become planets.

Explain what an accretion disk.

the material orbiting the star that will form the planets

Explain why certain elements and compounds are more prominently found at certain distances from the Sun

Lighter elements like H and He are more easily blown farther away from the Sun Complex compounds like H20 and CH4 (methane) get broken apart due to the Sun's radiation Heavier elements like Fe and silicates can be found through the system

Explain how the formation theory explains the terrestrial and Jovian planets and the asteroids and comets

High temps near the sun makes it difficult for hydrogen and helium to exist. when the sun 'turned on' it blasted away lighter materials/gasses leaving smaller rocky planets closest to it and larger gas giants further away. Asteroids & Comets are what is left over. Asteroids = more rocky than ice and therefore more closer to the sun, whereas Comets are more ice than rock and more are further from the sun.

Describe what happened during the period of heavy bombardment

it was approx. 100 million years where everything was colliding into everything. it created elements, brought water to earth.

describe the properties of the asteroid belt, Kuiper belt & Oort cloud.

Asteroid Belt: between Mars & Jupiter, made of rocky material that cannot form a planet due to Jupiter's gravitational pull when it nears the Belt on its orbit

Kuiper Belt: not enough rock/ice/gas past Neptune to form a planet

Oort Cloud: same as Kuiper Belt, even further out with less material.

Explain how radiometric dating works for calculating the age of our solar system.

measurement of an objects age based on the ratio of the parent atom and daughter isotope. in the case of our solar system, we measure the time since rock formed by measuring the proportions of atoms and isotopes in solidified rock. The decay has a half-life, which is the time it takes for half of the sample to decay.

Earth's Core

Highest density material with nickel and iron

Mantle

Moderate density with silicon, oxygen minerals

Crust

Granite basalts, lowest density

What are tectonic plates?

A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest.

Explain differentiation in relation to the formation of the Earth

Differentiation is where heavy stuff (Iron, nickel metal) sinks and less dense stuff (rock) rises. Forming the core and former layers.

Understand how to use the ideal gas law to describe our atmosphere

ideal gas law: PV=nRT

P: Presure (Pascals)

V: Volumne (m^3)

n: Number of mols (mols)

R: 8.314 J/Kmol

T: Temperature (Kelvin)

Pressure is directly proportional to temperature. When tem goes up, pressure is higher. Pressure is dependent on the composition of the gas in the atmosphere

Describe the history, changes and formation of our atmosphere

How it formed and changed:

the atmosphere is formed with the earth (primary atmosphere) sunlight heated the atmosphere. There was rapid thermal motion of light atoms and molecules caused which causeed the primary atmosphere to excape. Volcanoes on Earth released gases. Comets/asteroids impacted and brought water and other molecules to for the secondary atmostphere Earth's gravity was strong enough to keep the secondary atmosphere

Explain the greenhouse effect

Visible light comes from the sun through earth's atmosphere. some rays are reflected back into space, and some make ti to the surface. visible light that reached the surface is converted into infrared light which is then emitted off the surface of the earth. some infrared light escapes to space, and some are trapped by gasses in our atmosphere (CO2, H2O) and remain. These are 'greenhouse gasses' Temperature on earth is higher with the greenhouse effect than it would be should this cycle not occur. the amount of light absorbed/reflected is equal.

Convection

Convection is a way for heat to move, also referred to as a heat transfer mechanism.

Troposphere

Surface up to 7-17 km high Where weather comes from Warmed by Earth Greenhouse gasses are trapped in this layer Visible light passes through the surface

Stratosphere

From troposphere: 50-60 km Ozone layer Heated by UV light from the Sun No convection

Thermosphere

Heated by the Sun X-rays & UV & ionized gasses live here last layer they pass through

Exosphere

Outermost layer X-rays & UV live here they pass through here Fast-moving gas molecules escape from Earth here

Explain why the sky is blue and sunsets are red

The sky is blue because of preferential scattering: the particles in our atmosphere do a better job of scattering blue light than they do red light. The bluest parts of the sky are off to the sides from the Sun.

Sunsets are red because the sunlight passes “more atmosphere”. Most blue light is scattered away, leaving red light that gives the sky a reddish color.

Describe the Earth’s magnetic field and what generates it

A field that Protects the surface of the earth from charge particles and the solar winds from space. The requirements to generate a magnetic field are electrically conducting fluid, convection in that layer, moderately rapid rotation. The cooling and crystallization of the core stirs up the surrounding liquid iron, creating powerful electric currents that generate a magnetic field stretching far out into space. This magnetic field is known as the geodynamo.

Describe the magnetic field on the other terrestrial worlds in our Solar system

Venus and Mars don't have a significant magnetic field. Venus has too slow of rotation and mars has a solid core

Mercury doesn't have a significant magnetic field because Mercury has a huge metal core (solid) and has slow rotation.

Explain how earthquakes let us “see” inside of the Earth.

Primary waves (P waves): Longitudinal waves Travel through solid and liquid, and the waves alternating from compression and decompression like a spring.

Secondary waves (S waves): Transverse waves don't travel through liquid and they move along a length of a string.

The wave bend as they travel through different densities resulting in shadow areas, S waves have more shadow areas.

Explain the 4 ways in which the surface of a terrestrial planet can change

Impact Craters, Volcanism, Tectonics and Erosion. Asteroids & Comets can leave a surface cratered from impacts. Volcanoes can change the surface after eruptions as the magma cools and renews the surface. Tectonic plates can move entire continents creating a vast change on the surface. Erosion can cut through mountains and change the surface throughout a long period of time.

Explain the 3 reasons why the terrestrial planets differ

Size - Bigger planets stay warmer for longer, leads to more volcanism, outgassing and magnetic field.

Distance from the moon - Rain, snow, ice oceans and escape velocities, Tidal forces.

Rate of rotation - Drives wind and weather as well as magnetic field.

Describe a few orbital properties of specific planets

Mercury - orbiting the Sun faster than its rotational axis Venus - orbiting clockwise, is upside down Earth - orbit is tilted 23.5 degrees Mars - very similar to Earth, similar days and tilt but year is much longer

Describe a few geological properties of Mercury and the Moon

Mercury: Shrank due to cooling quickly after forming Has the most extreme day/night temperature changes in the solar system from the lack of atmosphere

Moon: Has an inactive core with no geological activity Previous lunar volcanic activity had thin lunar lava Similar material to the Earth's crust Far side has more craters than the closer side

Both: Lots of craters Negligible atmosphere

Describe a few properties of Venus and it’s atmosphere

Venus: Has a runaway greenhouse effect The atmosphere is mainly made up of carbon dioxide As much pressure as 90 Earth atmospheres, equivalent to being 1km underwater Surface is hotter than Mercury Relatively flat surface

Explain the difference between the greenhouse effect and the runaway greenhouse effect

The greenhouse effect is the trapping of infrared light within the atmosphere, leading to heating of the surface of a planet. (Ex.Earth) (See 9f for more detailed explanation).

The runaway greenhouse effect is an evolutionary process which starts from having a small greenhouse effect, and ends up with such a strong greenhouse effect that it self-produce more greenhouse gases; this leads to a stronger greenhouse effect, which then produces more gases. This lead to a significant increase in the temperature of the surface of planet. This effect is hard to stop. (Ex.Venus).

Describe a few properties of Mars

Mars Atmosphere: 1% of the Earth’s atmosphere, mostly CO2, but have very low greenhouse effect due to thin atmosphere.

-Similar tilt of the rotation axis to the one of Earth(25.2 degree), which leads to experiencing season like on Earth.

-Have polar caps made of dry ice and water ice.

-Most moons of the terrestrials planets (2 moons).

-Core: molten iron (from Insight Presentation)

Compare and contrast the atmospheres of the terrestrial worlds

Mercury: -composed of H, He -transient and tenuous

Venus: -composed of mostly CO2, and little bit of N2 -90 times denser than Earth

Earth: -78% N2, 21% O2

Mars: -Mostly CO2, and some N2 -1% thick as Earth’s atmosphere.