Cosmology Quiz March 27

how do you measure the cosmic elemental abundance

each element has unique orbital structure that leads to distinct emission and absorption lines. if you look at light from a nebulae, you see individual emission lines that tell you its composition. this is called spectroscopy

why is the cosmic elemental abundance important

it is a cosmic fingerprint, it helps us understand how stars form, origins of universe, and structures of planets and galaxies

what is the value of the elemental abundance of hydrogen, helium, and the sum of everything else

90% hydrogen, 9% helium, and 1% everything else

how does the temperature and energy density of the universe behave as it expands and contracts

as the universe expands, temp and energy density decrease, and vice versa. When space stretches, photons lose energy and cool down

what happens to an atom and a nucleus if you heat it enough

if you heat an atom enough, eventually the electron and nucleus will break free, and the nucleus will break into protons and neutrons. When the electron is stripped, that means the atom is ionized.

what is the era of particle physics

<1s

what is the era of nuclear physics

1s to 300000 years

what is the era of atomic and molecular physics

300000 years and onwards

what radiation is most dangerous

what is alpha radiation

low energy helium nuclei are ejected from an unstable atomic nuclei during radioactive decay. it has low penetration power and can be stopped by paper or skin, but is damaging if ingested

what is beta radiation

medium energy electrons are emitted during radioactive decay. it has moderate penetration power and can be stopped by aluminum or plastic, and can cause damage if absorbed

what is gamma radiation

high energy photons are emitted from an unstable nucleus after radioactive decay, it is highly penetrative and can cause serious biological damage, most harmful

explain the model of the atomic

most of the atom is empty space

size of the atom

ten to neg ten m

size of the nucleus

ten to neg fifteen m

how does a cloud chamber work to detect radiation

when vapor condenses along the tracks, these tracks can be bent using magnetic fields, and then energy can be measured that way

how does a geiger counter work to detect radiation

a tube is filled with gas, and when radiation enters the tube, the gas is ionized and pulses. the counter detects these pulses and counts them, thus providing a measure of radiation intensity

what is the form of the electric force law

force between 2 objects is proportional to product of their charges, and inverse to square of distance. Force is equal to couloumbs constant times the product of the charges divided by the distance squared

what is an isotope

a variant of an element that has the same number of protons but a different number of neutrons, resulting in a different atomic mass, or think of it as same atomic number and different neutrons, because atomic number, electrons, and protons should all be equal, can be formed by bombarding an element with neutrons

how do you determine the number of protons, neutrons, and electrons from the isotope symbol

protons are equal to the atomic number, and the electrons are equal to the number of protons. The number of neutrons is found by subtracting the atomic number from the mass number. Mass number will be written on top of atomic number

define the half life of an isotope

the time it takes for half of the atoms in a sample of a radioactive substance to decay

how do you use radioactive decays to date carbon base materials and rocks

carbon fourteen and potassium forty, how much of a sample remains, half life, and work backwards

how old is the earth

4.54 billion yrs

how old is the universe

13.8 billion yrs

what binds the nucleus

energy that comes from the difference between the mass of the nucleus and the mass of the parts, which holds protons and neutrons together despite repulsive forces between positively charged protons

what is binding energy

energy required to separate the particles in a nucleus, or the energy released when the nucleus is formed

what is the difference between nuclear fission and fusion

fission is the process where a heavy atomic nucleus splits into two smaller nuclei, releasing energy. fusion is the process where two light atomic nuclei combine to form a heavier nucleus, also releasing energy

what elements can be used for fission and fusion using the binding energy curve

for fission, uranium and plutonium are typically used because their large nuclei release a lot of energy and they have low binding energy, meaning they can split easily. for fusion, hydrogen isotopes are normally used because they have low binding energy and combining them releases energy, and when they combine the binding energy increases, which is why the process yields energy

how does the chain reaction in the process of nuclear fission work

when nuclei split into smaller nuclei, these nuclei can hit other nuclei and split as well, causing a chain reaction

what applications of fission and fusion are peaceful and non peaceful

peaceful applications include powerplants and medical radiation for fission, and energy research for fusion. non peaceful applications include atomic bombs for fission and hydrogen bombs for fusion

how does the expansion of the universe lead to the production of hydrogen and helium

big bang nucleosynthesis. the universe was hot and dense after big bang, which allowed protons and neutrons and protons to collide and form light elements. universe expanded and cooled, and protons combined to form hydrogen. some of these combined with neutrons to form helium. this all happened very quickly which is why those elements are 99% of the universe