Name & Seat #: ______Key____ March 24, 2000
 
 

Formulas and numbers that you may need:

Energy = mass x c^2

Waves speed: v=f l; Period: P=1/f

Photons energy: E=hf,

Doppler shift: Df/f=v/c

c = 3.0 x 10⁸ m/s; Speed of sound: cs = 340 m/s. h=6.6 x 10-34 J*s; 1 A.U. = 1.5 x 10^11 meter

Intensity = Power/Area

Area of a sphere = 4 pi r^2; Volume of a sphere = (4/3) pi r^3

From the observer’s triangle: Tan (alpha/2) = D/2L
 
 

Answer ALL 10 questions:
 
 

1. A car is sounding its horn, and 5 seconds later an echo from a mountain is heard. The distance to the mountain is

1. 1700 meter
2. 1.7 x 10^9 meter
3. 850 meter
4. 8.5 x 10^8 meter

1. The gravitational force on the surface of a white dwarf (mass identical to that of the sun, size identical to that of earth) is roughly______ than gravity on earth’s surface

1. 10 times larger
2. Million times larger

1. 3 times smaller
2. Billion times smaller

1. An interstellar gas cloud contracts to form a star. In the process

1. Heavy chamical elements become lighter elements
2. The cloud forms raindrops
3. The stars near that cloud become transparent
4. The cloud temperature increases

1. In gasses increased temperature results in

1. Increased pressure
2. Increased blackness
3. Increased conduction of magnetic flux
4. Decreased speed of sound

1. The star Betelgeuse is a

1. White dwarf
2. Red giant
3. Main sequence star
4. Planetary nebula

6. A red giant star of 1 solar mass emits ______ power than the sun

1. More
2. Less
3. The same

1. The center of the sun must be very hot in order to

1. Have enough pressure to counteract the gravitational pull
2. Maintain nuclear fusion reactions
3. Both a and b
4. None of the above

1. If a star is massive enough nuclear fusion in its core may result in helium fusion into carbon and oxygen. If the temperature of the core is hot enough ____________ may form from the fusion of carbon and oxygen nuclei.

1. Nitrogen
2. Hydrogen
3. Uranium
4. Silicone

1. In a supernova the pressure that throws the outer layers may be the result of

1. Massive out-flux of neutrinos
2. Explosive fusion of helium in the outer core
3. Over cooling of the hydrogen shell
4. Gravitational pull by nearby stars

a. The radius of that star is smaller than 10,000 km.

b. The surface temperature of that star is smaller than 5000 K.

1. The mass of the star is larger than 1.5 the mass of the sun.
2. The surface of the star is made of sulfuric acid.

10. Neutron stars form when the iron core of a massive collapses and

1. protons change into electrons, neutrons and neutrinos
2. protons change into anti electrons, neutrons and neutrinos
3. protons change into neutrons, gamma rays and neutrinos