Tuesday, October 20, 2009

Black Holes and the Big Bang Theory

Black holes (picture on left) - are theorized to form when a massive star collapses at the end of its life. Centers of galaxies contain black holes. The gravitational field of a black hole is so great that not even light can escape from a black hole.

Big Bang Theory- the theory that proposes the Universe originated from a state of high temperature and density. This theory says the Universe began about 13.75 billion years ago. One piece of evidence of the Big Bang theory is the existence of cosmic background radiation (top picture). This radiation, from all directions in the sky, is said to be left over from the big bang.

Milky Way Galaxy

The Milky Way is the galaxy which contains our Sun. Our Sun is located within one of the spiral arms. Our galaxy is a collection of stars and interstellar dust. This dust/matter known as a nebula is the birthplace of stars. gravity is the force which pulls this matter together.
The average distance between stars in our part of the galaxy is 5 light-years. A light-year measures distances between interstellar objects (the distance light travels in one year).


The two basic types of lens are pictured to the left. Top lens is a convex ( converging lens). Bottom lens is a concave (diverging lens).

Convex lens- magnifies, enlarges, image is inverted.

Concave lens- diverging, spreads light apart, image is reduced.


Diffraction- the slight bending of a wave around the edge of an obstacle in its path.

H-R Diagram

The Hertzsprung-Russell (H-R) diagram shows the relationship between temperature and absolute magnitude.

  • 90% of all stars are main sequence stars
  • blue stars have the highest surface temperatures
  • the brightest main-sequence stars are also the hottest.
  • the Sun is an average main sequence star, yellow in color
  • as our Sun ages it will eventually become a red giant
  • the Sun has an absolute magnitude of +5

Our Sun

Our Sun and solar system was formed from a huge cloud of dust and gases that condensed due to the force of gravity.
Scientists by studying the Sun's or any star's spectrum can determine the chemical composition of that star. Our Sun is composed of 71% hydrogen, 27% helium and 2% heavier elements.

The Sun's energy is produced by nuclear fusion. This process combines, fuses, hydrogen atoms into helium atoms. Some mass is lost during this process and transformed into energy. This energy is radiated into space as the EM spectrum and the solar wind.

The solar wind is a stream of electrons and protons which are emitted from the Sun's corona. The corona is the outer gas layer of the Sun seen during solar eclipses.

The Sun is a large nuclear fusion reactor that has enough fuel, hydrogen, to burn for approximately another 5.5 billion years. Our Sun like all stars will eventually run out of fuel, hydrogen, and collapse.

Doppler Effect Sound and Light


Check this link about the Doppler effect.

Sound Waves

Sound Waves:
  • sound needs a medium to travel through
  • the sound wave is a compressional wave
  • the particles of the wave are compressed, then released, thing of a Slinky

Bats use ultrasound (above human hearing) to locate food sources- bugs. This process is known as echolocation.

Sonar- the process of reflecting sound waves underwater to locate objects.

Sunday, October 18, 2009

Concave Mirrors & Light

Concave mirrors- like the bowl of a spoon. The image formed is enlarged and upright.

We can see object because light is being reflected from those objects. The color of the object depends on the frequency of light being reflected. White light ( which contains all colors, think prism) when striking an object will absorb some of the colors, while reflecting back others- we see reflected light.

Refraction of light- as light travels from one medium to another it will change speeds, object appears to be bent.


Mirror- any smooth object that reflects light to form an image.

Plane mirror
  • angle of incidence = angle of reflection
  • image is virtual
  • image is "behind" the mirror the same distance as it is in front of the mirror.

Convex mirror- light rays diverge (spread apart) greater field of view. Automobile outside mirrors are convex mirrors.

Physical Science Waves

Electromagnetic Waves- electric and magnetic field that are perpendicular to each other.

  • transverse waves
  • do not need a medium
  • light is a EM wave
  • light is a combination of a wave and particle
  • photon- packet of energy/ particle that carries energy.
  • waves will travel as long as there is energy to carry
wave speed = frequency x wavelength
  • wave speed (ws) is measured in m/s
  • frequency (f) is measured in hertz
  • wavelength is measured in meters
  • the speed of a light wave is a constant in a vacuum (symbol "c") is 300.000 km/s
  • speed of a EM wave will decrease as it enters a more dense medium
  • the higher frequency EM waves will have short wavelengths, low frequency will have longer wavelengths.
  • gamma rays have the the shortest wavelength/ highest frequency.
  • EM spectrum ( low frequency to high)- radio, infrared, visible, x-ray, gamma.

Tuesday, October 13, 2009

Chem Chap 3 Review

Standard Metric Units

  • mass- kilogram, kg
  • volume- liter, L
  • length- meter, m
  • time- second, s
  • temperature - Kelvin, K- neat thing about Kelvins no negative values, cannot get colder than absolute zero.
Weight- is the pull of gravity on an objects mass, therefore weight is dependent on gravity. Another way to look at this is an objects position, location, from a source of gravity. Farther away from gravity object will weigh less.

Density- is an intensive property of the object, that is it does not depend on the "amount" of the object. D=mass/volume. Be sure you can calculate for any variable in the density formula. Refer back to your worksheet for problems.

Factor-Label Method- be sure to review this. 100cm= 1m, therefore it also can be written:
1m/100cm or 100cm/1m.

Scientific notation
  • when moving decimal to the right- negative exponent
  • when moving decimal to the left- positive exponent
  • after moving decimal only one number to the left of the decimal point.
  • when multiplying add exponents, dividing subtract
ex: 0.0000045 4.5 x10 -6
450000 4.5 x10 5 ( -6 and 5 are exponents)
3 x 10 3 X 4 x 10 -6 12 x 10 3 +(-6) 12 x 10 -3 1.2 x 10 -2
8 x 10 4 / 2 x 10 -5 4 x 10 4 - (-5) 4 x 10 9

Significant Figures

Refer to rules in your notebook. In multiplication and division your answer can only have as many sig figs as the least precise number ( lowest number of sig figs)

ex. 0.001 1 SF
0.00100 3 SF
0.001001 4 SF
100 1 SF
101 3 SF
101.0 4 SF

Sunday, October 4, 2009

Physical Science Review

For the test Friday be sure to review:
  • your packet on Topographic Maps.
  • diagrams of solar and lunar eclipses
  • how to calculate speed
  • scientific notation
  • factor-label conversions
  • metric relationships
  • Newton's Laws of Motion
  • difference between mass and weight
  • rotation- spinning on axis, causes night and day
  • revolution- orbit around the Sun
  • cause of the seasons- tilt of the Earth on its axis
Famous astronomers:
  • Ptolemy- proposed the geocentric model of the universe
  • Copernicus- given credit for the heliocentric model of the solar system
  • Galileo- inventor of telescope
  • Kepler- discover elliptical shape of planetary orbits.
  • Newton- discovered forces that keep planets in orbits
Moon Info
  • period of rotation and revolution are the same- 27 1/3 days
  • moon has no atmosphere therefore, no weathering, craters are present
  • age of moon is the same age as the Earth
  • waxing- new to full moon
  • waning- full to new moon
  • takes the moon about 4 weeks to go through a full cycle