Physics #9

Question 1

photoelectric effect

Answer 1

when light with sufficiently high frequency is incident on a metal in a vacuum, the metal atoms emit electrons

Question 2

what do ions released by the photoelectric effect product?

Answer 2

current

Question 3

when the light’s frequency is above the threshold frequency, the magnitude of the resulting current is directly proportional to _____

Answer 3

the intensity (and amplitude) of the light beam

Question 4

threshold frequency

Answer 4

the minimum frequency of light that causes ejection of electrons

Question 5

why is the photoelectric effect an all or nothing response

Answer 5

if the frequency of the incident photon is less than the threshold frequency, then no electron will be ejected because the photons do not have sufficient energy to dislodge the electron from its atom

Question 6

when is the maximum kinetic energy of an ejected electron achieved?

Answer 6

when all possible energy from the photon is transferred to the ejected electron.

Question 7

in the photoelectric effect, is the speed of ejected electrons dependent on the frequency of light or its intensity?

Answer 7

frequency

the number of electrons ejected depends on intensity

Question 8

Borh model of atom

Answer 8

electron energy levels are stable and discrete, corresponding to specific orbits

Question 9

IR spectroscopy

Answer 9

determine chemical structure because different bonds will absorb different wavelengths

Question 10

we see the colors that are ___ absorbed

Answer 10

not

Question 11

T/F: small changes in chemical structure minimally impact light absorption and emission patterns

Answer 11

false

just protonating a structure can make a huge difference in absorptions patterns (phenylthaline)

Question 12

how does fluorescence occur?

Answer 12

fluorescent substance excited with ultraviolet radiation and then the electrons step-wise fall back down which releases lower energy photons in the visible range.

Question 13

the mass of every nucleus is ______ than the mass of protons and neutrons combines

Answer 13

smaller

Question 14

mass defect

Answer 14

the mass of every nucleus is smaller than the mass of protons and neutrons combines

the result of matter that has been converted to energy.

Question 15

strong nuclear force

Answer 15

the attraction between the protons and neutrons in the nucleus which overcomes the repulsive electromagnetic force between the protons

releases energy which is the mass defect

Question 16

what size nuclei are the most stable?

Answer 16

intermediate size

Question 17

what are the 4 fundamental forces of nature?

Answer 17

strong nuclear force
weak nuclear force
electrostatic forces
gravitation

Question 18

fusion

Answer 18

when small nuclei combine to form a larger nucleus

Question 19

fission

Answer 19

a process by which a large nucleus splits into smaller nuclei

Question 20

does spontaneous fission occur a lot?

Answer 20

no

Question 21

radioactive decay

Answer 21

a naturally occurring spontaneous decay of certain nuclei accompanied by the emission of specific particles

Question 22

discuss alpha particles and lead sheets

Answer 22

alpha particles interact with matter very easily, hence they do not penetrate shielding such as lead sheets

Question 23

do alpha particles carry any charge?

Answer 23

yes, +2 because they have 2 protons and do not carry any electrons

Question 24

where does the electron come from for beta decay?

Answer 24

electrons do not reside in the nucleus, but they are emitted by the nucleus when a neutron decays into a proton, a beta particle, and a antineutrino

Question 25

is beta particle or alpha particle more penetrating?

Answer 25

beta particle

Question 26

what does positron decay release?

Answer 26

neutrino and positron

Question 27

what do gamma rays do?

Answer 27

high-energy, high-frequency photons. They carry no charge and simply lower the energy of the parent nucleus without changing the mass number or the atomic number

Question 28

do gamma rays have a charge?

Answer 28

no

Question 29

electron capture

Answer 29

unstable radionuclides are capable of capturing an inner electron that combines with a proton to form a neutron, while releasing a neutrino.

Question 30

half-life

Answer 30

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

Question 31

how many nuclei are there per mole of a sample

Answer 31

avogadro’s: 6.022 x 10^23

Question 32

does nuclear fusion or nuclear fission release energy?

Answer 32

both

Question 33

does positron or beta decay release antineutrino?

Answer 33

beta decay

Question 34

beta-negative decay and beta-positive decay are the correct terms

Answer 34

nice

Question 35

what type of nuclear decay can be detected in an atomic absorption spectrum?

Answer 35

gamma: releases electromagnetic radiation rather than nuclear fragments.

Question 36

compare fusion and fission

Answer 36

fusion: combining
fission: breaking down

Question 37

T/F: for an electron to jump to a higher energy level it has to absorb the exact frequency of energy that puts it there

Answer 37

True

Question 38

why is energy released in both nuclear fusion and fission?

Answer 38

the nuclei that are formed are more stable (energy was released)

Question 39

an alpha particle is a ____ nucleus

Answer 39

helium

Question 40

to jump energy levels, need ______ amount of energy absorbed

Answer 40

exact

Question 41

all light travels at ______

Answer 41

speed of light