AST201 week 4

the sun generates energy by slowly contracting in size, a gradually shrinking sun would always have some gas moving inward converting gravitation potential energy into thermal energy

gravitational equilibrium and energy balance

between outward push of internal gas pressure and the inward pull of gravity

between the rate of which fusion releases energy in the sun’s core and the rate at which the sun’s surface radiates this energy into space

the sun will finally exhaust its nuclear fuel and gravitational contraction will begin once again

visible splotches that appear darker than the surrounding surface (larger in life than earth)

the rate at which energy is used or released

a stars total power output

stream of charged particles continually blown outward in all directions from the sun

outermost layer of the atmosphere, temp is astonishingly high, density is very low

middle layer of the solar atmosphere and the region that radiates most of the sun’s UV light

lowest layer of the atmosphere, visible surface of the earth

where energy generated in the solar core travels upward, transported by the rising of hot gas and falling of cool gas called convection

where energy moves outward primarily in the form of photons of light, turbulence of convection zone gives way to the calmer plasma

source of suns energy, density is more than 100 times that of water, extreme pressure

the energy that light carries

the unit we measure energy in

the rate of energy flow, measured in units called watts

a prism split light into the rainbows of light

a mix of all these colours in roughly equal proportions

when we perceive no light and hence no colour

red, green, blue (RGB)

emission, absorption, reflection

materials which transmit light

materials that absorb light

can sit still or move from one place to another

consist of peaks

distance from one peak to the next

number of peaks passing by any point each second

another name for cycles per second

describe the strength of force that a particle would experience at any point in space

light waves are traveling vibrations of both electric and magnetic fields

light comes in individual “pieces” that have properties of both particles and waves

light that we can see

light itself

light that we can see with the naked eye

light with wavelengths somewhat longer than those of red light

lies between blue and end of the rainbow in wavelengths

all ordinary matter is composed of atoms

atoms come in different types and each type corresponds to a different chemical element

• protons

• neutrons

• electrons

• nucleus

oppositely charged particles attract and similarly charged particles repel

number of different material substances is far greater than the number of chemical elements because atoms can combine to form molecules

interactions between electrons that hold the atoms in a molecule together

high enough temp, the collisions become so violent they break chemical bonds

force per unit area pushing on an objects surface

the possible energy of an atom

an electron can rise from a low energy level to a higher one, or fall from a high level to a lower level

the process of obtaining a spectrum and reading the info it contains

1. continuous spectrum

2. emission line spectrum

3. absorption line spectrum

the spectrum of a traditional, or incandescent, light bulb is a rainbow of colour, because the rainbow spans a brand range of wavelengths without interruption

a thin or low density cloud of gas emits light only at a specific wavelengths that depend on its composition and temp, the spectrum consists of bright emission lines against a black background

cloud of gas lies between us and a lightbulb, still see most of the continuous spectrum of the light bulb, but the cloud absorbs light of specific wavelengths, so the spectrum shows dark absorption lines over the background rainbow

1. each square metre of a hotters object surface emits more light at all wavelengths

2. hotter objects emit photons with a higher average energy

if an object is moving toward us the light waves bunch up and its entire spectrum is shifted shorter wavelengths

diameter is 100 times Earth’s diameter

8 light minutes from Earth

showed that the sun was made mostly of hydrogen, a little helium, and tiny amounts of other elements

the wavelength of light determines its colour and energy

bluer (and more energetic)

low energy (700 nm)

high energy (400 nm)

a continuous spectrum: it has some of every colour of light

emit a special kind of continuous spectrum

the amount of light given off by a blackbody and the wavelength where it emits the most light set by the temp of the blackbody

it emits more light

the wavelength at which it emits the most light shifts to shorter wavelengths

tell us what the sun and other stars are made of

absorbing light

different sets of orbitals

emitting light

transitions between orbitals do

blackbodies or “thermal emitters”

on fire, it is mainly made of hydrogen

a gas that is so hot, the electrons break free from the atoms

the sun is in this, the pressure pushing outwards and the gravity pulling inwards is balanced

5800 K

15 million K

the reaction between energy and mass

convert matter to energy (or the reverse)

hydrogen is being converted into helium via nuclear fusion

providing enough outward pressure necessary to support stars against collapse

only interact with other matter via the weak nuclear force and gravity, can pass through objects that are very large and dense

respond to the electromagnetic force, so they dont interact with most matter