Untitled Flashcard Set

When light slows down entering a new medium, it bends __.

toward the normal.

When light speeds up entering a new medium, it bends __.

away from the normal.

What does the law of reflection state?

Angle of incidence equals angle of reflection.

Diffuse reflection is the __ of light from a rough surface.

scattering

Fermat’s Principle states that light takes the __.

path of least time.

Why does the Sun appear higher at sunrise and sunset?

Atmospheric refraction bends sunlight.

Why do stars twinkle?

Turbulent air refracts starlight unpredictably.

The cause of a mirage is __.

total internal reflection in hot, less dense air.

Total internal reflection occurs when the angle is greater than the __.

critical angle going from dense to less dense.

The index of refraction formula is __.

n = c / v.

The sky appears blue because __.

short wavelengths scatter most.

Why are sunsets red?

Blue light scatters away over long paths; red survives.

Clouds appear white because __.

water droplets scatter all visible wavelengths.

The cause of a rainbow involves __ and internal reflection inside raindrops.

dispersion

Thin film interference is caused by __.

interference between reflections from top and bottom surfaces of a thin film.

Why do soap bubbles show colors?

Thin film interference.

What determines the colors in thin films?

Film thickness and wavelength of light.

Fluorescence occurs when __ excites electrons which emit visible light.

UV light

Fluorescent lamps use phosphor to __.

convert UV light to visible light.

The main difference between fluorescence and phosphorescence is that phosphorescence emits light __.

slowly due to metastable states.

What is an emission spectrum?

Bright lines emitted by excited atoms.

An absorption spectrum is characterized by __ where atoms absorb specific wavelengths.

dark lines

Alpha radiation is a __.

helium nucleus (2 protons, 2 neutrons).

What changes occur during alpha decay?

Atomic number –2, mass number –4.

Beta minus decay changes the atomic number by __.

+1, mass number unchanged.

Gamma emission results in __.

no change in atomic or mass number.

The highest penetrating radiation is __.

gamma radiation.

The strong nuclear force is the __ force and binds nucleons.

strongest and short-range

Why are large nuclei unstable?

Strong force weakens at long distances; proton repulsion increases.

A free neutron behavior results in __.

beta decay into proton, electron, and antineutrino.

Radioactivity is the __ of unstable nuclei.

spontaneous decay

Half-life is the time for __ of a radioactive sample to decay.

half

The type of radiation used in smoke detectors is __.

alpha radiation.

Nuclear fission is the __ of a heavy nucleus into smaller ones with energy release.

splitting

The main source of fission energy comes from __.

kinetic energy of fission fragments.

A condition necessary for a chain reaction is __.

critical mass.

The function of a moderator in nuclear reactions is to __ neutrons.

slow.

Control rods function to __ neutrons.

absorb.

The function of a coolant in a reactor is to __.

transfer heat from the reactor core.

A breeder reactor produces __ by converting U-238 into Pu-239.

plutonium

Nuclear fusion involves the __ of light nuclei into heavier nuclei with energy release.

joining

In the Sun, hydrogen fuses into __.

helium.

Fusion releases energy because __ decreases.

mass per nucleon.

In both fission and fusion, what is conserved?

The number of nucleons.

The fastest-moving radiation is __.

gamma.

Who explained nuclear fission?

Lise Meitner.

Mass-energy equivalence is represented by the equation __.

E = mc².

The photon energy equation is __.

E = hf.

The wave speed formula is __.

v = fλ.

Absorption lines are caused by __ of specific frequencies of light.

atoms absorbing.

When light slows down entering a new medium

It bends toward the normal.

When light speeds up entering a new medium

It bends away from the normal.

Law of reflection

Angle of incidence equals angle of reflection.

Diffuse reflection

Scattering of light from a rough surface.

Fermat’s Principle

Light takes the path of least time.

Why the Sun appears higher at sunrise/sunset

Atmospheric refraction bends sunlight.

Why stars twinkle

Turbulent air refracts starlight unpredictably.

Cause of a mirage

Total internal reflection in hot, less dense air.

Total internal reflection

Occurs when angle > critical angle going dense to less dense.

Index of refraction formula

$$n = \frac{c}{v}$$

Why the sky is blue

Short wavelengths scatter most.

Why sunsets are red

Blue light scatters away over long paths; red survives.

Why clouds are white

Water droplets scatter all visible wavelengths.

Cause of a rainbow

Dispersion + internal reflection inside raindrops.

Cause of thin film interference

Interference between reflections from top and bottom surfaces of a thin film.

Why soap bubbles show colors

Thin film interference.

What determines thin film colors

Film thickness and wavelength of light.

Fluorescence

UV excites electrons which emit visible light.

Why fluorescent lamps use phosphor

Converts UV light to visible light.

Difference between fluorescence and phosphorescence

Phosphorescence emits light slowly due to metastable states.

Emission spectrum

Bright lines emitted by excited atoms.

Absorption spectrum

Dark lines where atoms absorb specific wavelengths.

Alpha radiation

Helium nucleus (2 protons, 2 neutrons).

Alpha decay changes

Atomic number $-2$, mass number $-4$.

Beta minus decay changes

Atomic number $+1$, mass number unchanged.

Gamma emission changes

No change in atomic or mass number.

Highest penetrating radiation

Gamma radiation.

Strong nuclear force

Short-range but strongest force; binds nucleons.

Why large nuclei are unstable

Strong force weakens at long distances; proton repulsion increases.

Free neutron behavior

Beta decays into proton, electron, and antineutrino.

Radioactivity

Spontaneous decay of unstable nuclei.

Half-life

Time for half the radioactive sample to decay.

Radiation used in smoke detectors

Alpha radiation.

Nuclear fission

Splitting a heavy nucleus into smaller ones with energy release.

Main source of fission energy

Kinetic energy of fission fragments.

Condition for chain reaction

Critical mass.

Moderator function

Slows neutrons.

Control rods function

Absorb neutrons.

Coolant function

Transfers heat from the reactor core.

Breeder reactor production

Converts $\text{U-238}$ into $\text{Pu-239}$.

Nuclear fusion

Joining light nuclei into heavier nuclei with energy release.

Fusion in the Sun

Hydrogen fuses into helium.

Why fusion releases energy

Mass per nucleon decreases.

What is conserved in fission and fusion

Number of nucleons.

Fastest-moving radiation

Gamma.

Scientist who explained nuclear fission

Lise Meitner.

Mass–energy equivalence

$$E = mc^2$$

Photon energy equation

$$E = hf$$

Wave speed formula

$$v = f\lambda$$

Cause of absorption lines

Atoms absorb specific frequencies of light.