A 105 Exam 2
Describe the properties and everyday uses of CCDs? - correct answer
✔CCDs contain millions of pixels. They are much more sensitive than
photographic plates and are now used in mosaics, by astronomers, to cover a
large field on the sky. Their everyday uses are in digital cameras and cell
phones.
How does the resolution of a telescope above the atmosphere depend on the
size of the mirror? - correct answer ✔The larger the mirror, the better the
resolution, i.e the sharper the images.
How much larger is the sun than the earth in diameter? In volume? - correct
answer ✔the sun diameter is 100x bigger than the earth,
Volume = 10^6 x the diameter of the earth
What is the average density of the Sun?How does this compare with water? -
correct answer ✔density = 1400 kg/m^3
water is 1000 kg/m^3
What is hydro static equilibrium for the Sun? - correct answer ✔Hydro static
equilibrium is a balance between the outward gas pressure force in the Sun
and the inward pull of gravity. The Sun supports its own weight by its outward
gas pressure force, so that it is neither contracting nor expanding
What is thermal equilibrium for the Sun? - correct answer ✔Thermal
equilibrium is a state in which the energy radiated by the photo sphere of the
Sun is replaced by an internal energy source, nuclear fusion in the core.
, What are the central and surface temperatures of the Sun? - correct answer
✔Central temp = 1.6 x 10^7 K
photo sphere is 5800k
What are the two most abundant elements in the Sun? - correct answer
✔Hydrogen and helium also in the universe
What is the physical state of the material in the Sun? - correct answer
✔ionized state, electrons move freely rather than being bound to a particular
nucleus
What type of particle is a normal hydrogen nucleus? - correct answer
✔proton
What is the energy source of the Sun? - correct answer ✔thermonuclear
fusion of hydrogen to helium in its core
Physical process of thermonuclear fusion how it releases energy? - correct
answer ✔Through a series of reactions. four hydrogen nuclei are fused to
produce one helium nucleus plus energy. the mass of normal helium nucleus
is slightly less than four times the mass of a normal hydrogen nucleus. The
most mass is converted to an equivalent amount of energy according to the
relation E = mc^2.
Discuss where this process occurs in the Sun and why its occurs there? -
correct answer ✔Nuclear fusion occurs only in the core of the Sun, since it is
only there that the temperature is sufficiently high (T>10^7 k). High
temperature is required for nuclear fusion, since nuclei must collide at high
speed in order to overcome their electrical repulsion.
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