Lec 10 Flashcards
(19 cards)
electrical charge
The properties of an atom depend mainly on the electrical charge in its nucleus.
Electrical charge is a fundamental physical property that describes how strongly an
object will interact with electromagnetic fields; total electrical charge is always conserved, just as energy is always
conserved.
e.g +1
molecules
atoms can combine to form molecules. Some molecules
consist of two or more atoms of the same element
chemical bond
interactions between electrons that hold the atoms in a molecule together. For example, we say that chemical bonds hold the hydrogen and
oxygen atoms together in a molecule of H O
molecular dissociation
At high enough temperatures, the collisions become
so violent that they can break the chemical bonds holding
individual water molecules together.
The molecules then
split into pieces, a process we call molecular dissociation.
(In the case of water, molecular dissociation usually frees
one hydrogen atom and leaves a negatively charged molecule that consists of one hydrogen atom and one oxygen
atom
ionization
process of
stripping electrons from atoms is called ionization
plasma
This type of hot gas, in which atoms
have become ionized, is called a plasma.
pressure
Pressure is the force per
unit area pushing on an object’s surface. You feel more pressure when you squeeze your arm because squeezing increases the force on each square centimeter of your
arm’s surface.
energy levels
Only a few particular energies are
possible; energies between these special few are not possible.
The possible energies are known as the energy levels of an atom
energy level transitions
An electron can rise from a low energy level to a higher one or fall from a high level to
a lower one.
Such changes are called energy level transitions
solar prominences
Sunspots tend to occur in pairs, connected by a loop of magnetic field lines that can arc high above the Sun’s
surface
Gas in the Sun’s chromosphere
and corona becomes trapped in these giant loops, called
solar prominences.
coronal holes
regions of the corona
barely show up in x-ray images; these regions, called coronal
holes, are nearly devoid of hot coronal gas
coronal mass ejections
These particles
travel outward from the Sun in huge bubbles called coronal
mass ejection
sunspot cycle
The most notable pattern in solar
activity is the sunspot cycle—a cycle in which the average
number of sunspots on the Sun gradually rises and falls
At the time of solar maximum, when sunspots are most numerous, we may see dozens of sunspots
on the Sun at one time.
In contrast, we may see few if any sunspots at the time of solar minimum
sunspot formation
The locations of sunspots on
the Sun also vary with the sunspot cycle
As a cycle begins at solar minimum, sunspots form primarily at
mid-latitudes (30° to 40°) on the Sun.
The sunspots tend to
form at lower latitudes as the cycle progresses, appearing very close to the solar equator as the next solar minimum
approaches.
Then the sunspots of the next cycle begin to
form near mid-latitudes again
cause of the sunspot cycle
The precise reasons for
the sunspot cycle are not fully understood, but the leading
model ties it to a combination of convection and the Sun’s rotation.
Convection is thought to dredge up weak magnetic fields generated in the solar interior, amplifying them as they rise.
The Sun’s rotation—faster at its equator than near its poles—then stretches and shapes these fields.
what causes solar activity?
Sunspots and other changing features of the Sun constitute solar activity, which is
caused by strong magnetic fields that contort and sometimes snap, creating phenomena that include flares, prominences, and coronal mass ejections.
The magnetic fields also carry energy upward,
depositing the heat that explains the high temperatures of
the chromosphere and corona.
how does solar activity vary with time?
The sunspot cycle, or the variation in the number of sunspots on the Sun’s surface, has an average period of 11 years.
The magnetic field flip-flops every 11 years or so, resulting in a 22-year magnetic cycle
The sunspot cycle and other solar activity are
tied to the Sun’s ever-changing magnetic field, which is created by the combination of convection and the Sun’s rotation pattern (faster at the equator than at the poles).
rods
(in eye) measure brightness of colours
-tells us how much light there is
cones
tells us what colour of light we see
-diff cones are sensitive to diff energies of light (long vs short wavelengths)
