Atomic and Nuclear Phenomena Flashcards
1
Q
photoelectric effect
A
- when a sufficiently high frequency light (usually blue-UV) is incident on a metal in a vacuum, the metal atoms emit electrons
- these freed electrons will then produce a net charge flor per unit time, a current
- greater light beam intensity (amplitude) above threshold produce larger current, greater photons fall in electrode and greater liberated electrons
2
Q
threshold frequency
A
- fT
- depends on metal type
3
Q
energy of a photon
A
E = hf
h: 6.626 x 10^-34 J•s
4
Q
kinetic energy of ejected electrons
A
Kmax = hf - W
- only achieved when all possible energy from the photon is transferred to the ejected electron
5
Q
Work function of an electron
A
W = hfT
6
Q
fluorescence
A
- upon excitation of a fluorescent substance w UV radiation it will begin to glow in visible light
- when electrons returns to original state in 2 or more steps, each step involves less energy and thus the photon emitted has lower frequency than UV absorbed
7
Q
mass defect of the nucleus
A
E = mc^2
8
Q
mass defect is the result of…
A
- matter that has been converted to energy
- a very small amount of mass will yield a huge amount of energy
- 1 TJ = 10^12 J
9
Q
nucleons and strong nuclear force
A
protons + neutrons
- attracted to one another by a strong nuclear force, compensates for the repulsive electromagnetic force between protons
- acts over extremely short distances
10
Q
binding energy
A
- bonded system at a lower energy level than unbonded
- allows the nucleons to bind together in the nucleus
- the amount of mass that is transformed into dissipated energy will be a measurable fraction of the initial total mass
- binding energy per nucleon peaks at iron (most stable nucleus)
- intermediate sized nuclei are more stable than very large or small nuclei
11
Q
weak nuclear force
A
- also contributes to the stability of the nucleus
- but it’s about one millionth a strong as the strong nuclear force
12
Q
fusion
A
- small nuclei combine to form a larger nucleus
13
Q
fission
A
- large nucleus split into smaller nuclei
- rarely occurs spontaneously
- absorption of low energy neutron, fission can be induced in certain nuclei
- of special interest are fission reactions that release more neutrons because these other neutrons will cause a chain reaction in which other nearby atoms can undergo fission; this in then releases more neutrons, continuing the chain rxn
14
Q
radioactive decay
A
- spontaneous decay of certain nuclei accompanied by the emission of specific particles
15
Q
balancing nuclear reactions…
A
sum if atomic numbers must be same on both sides
