PHYS 200 Final, Fall 1999

Physics Department Physics 200 ~ Feb. 4, 2000 Final Exam Time:1 12 hours Name: LD No.: cross the name of your instructor: Isber Information: No make up for this exam without legal reason. Only one answer is valid for multiple choice questions. All questions are obligatory Physical constants: the speed of light is c=3 x 10° m/s Gravitational constant G = 6.67 x 197! mi/kg.s” Mass of the sun M,=2 x 10°°kg 1 parsec (PC) = 3.26 light year (ly) Planck’s constant h = 6.626x10"* J.s Grade True or False True False — e The sidereal day is based on the rotation Lf of the Earth with respect to distant stars. e¢ When a particular event happens, Beirut : clocks indicate 2 hours later than Greenwhich clocks. ‘|G e Seismic transverse waves (s-waves) cannot travel through (J a liquid. e The celestial coordinate corresponding to latitude on earth is called right ascension. e The occasion when the sun crosses the celestial equator is called solstice. e Kepler’s third law is relation between the period é of rotation of a planet and the planet’s diameter. e The central temperature of the Sun is less than 107K e Earth’s atmosphere is composed primarily of oxygen e The lifetime of a star depends on its initial temperature ‘ and radius. & e In order for hydrogen fusion to occur, the temperature must be about 100,000 K. e The energy of a photon of wavelength 2 is two times bigger than these of a photon of wavelength 4/2. e The amount of the doppler shift varies with the inverse of the velocity. e A 6-meter diameter telescope will collect 9 times More light than a 2-meter diameter telescope. yo 4 Multiple choices. When the Earth is between the sun and the moon, what kind of eclipse viewed from the earth can occur? a) total solar eclipse b) partial solar eclipse c) annular solar eclipse d) lunar eclipse If the wave’s frequency increases by a factor of 3, by what factor would the wavelength change? a) three b) one (no change) c) one ninth d) one third The star Altair is a Bla star with a surface temperature of 8000k. Its apparent magnitude is m = +0.77 and its distance is 16.5 light years. (a) The absolute magnitude of Altair is: Answer: (b) What kind of star is this? Main sequence star red giant red dwarf blue supergiant (c) Assuming that this stars emits like a black body, what is the maximum wavelength of its radiation? Answer: a (A) What kind of object is formed after a supernovae? a) ared giant star b) a white dwarf c) aneutron stars d) a black hole ‘e) either c) or d) depending on the mass of the star. A star has a distance of 10 parsecs. What is its parallax? 10 minutes of arc 10 seconds of are |_J0.1 seconds of are 0.01 seconds of arc The radius of the solar system is about 40AU. The time for the light to cover this distance is about 4 min 40 min 1600 min 32 min none of the above, my answer is i In the adjacent figure which line indicates the direction of the force of gravity on the earth as it orbits the sun. a. b. What time of the year does the figure on the right represent for the northern hemisphere. vernal equinox spring equinox winter solstice summer solstice What gas in the Earth’s atmosphere absorbs ultraviolet radiation from the sun? J carbon dixoide nitrogen oxygen ozone If two stars have the same surface area, but one star has 3 times the temperature of the other. How many times more energy is radiated by the hotter star? a)3 b) 12 c)9 da) 81 e) 27 In the figure on the right, 6 stars are lined up at 10 parseconds with their given apparent magnitude at that distance. Sy m which star could be the sun? m= 1 2 3 4 5 6 oe S Ss ~ m= 2 4 m= 9 Which star has 100 times the luminosity of the sun? 3\ 1 2 3 4 5 6 Jo Pe 2B m=l0 c) what is the absolute magnitude of star 2? 4 & m=-2 a) -10 | b) +1 c) 10 d) —0.02 e) 0.0004 The table below shows some properties of various stars. On the basis of these data answer the following questions (a) to (f) Absolute Apparent Spectral Type Magnitude (M)} Magnitude (m) -1.13 1.65 -7.2 1.25 Mirfak 2.2 1.79 Betelgeuse -7.0 0.50 (a) Which star is intrinsically the brightest (b) Which star has the greatest apparent magnitude (c) Which star has the greatest surface temperature (d) Which star is a reddish supergiant? (e) What is the distance of the star Betelgeuse from us? (f) The star Elnath has a parallax of 0.028 arc sec. What is its distance from Earth? Answer : parsec The sun gets its energy supply from: a) Slow contraction b) Nuclear fusion of oxygen in the core c) Nuclear fusion of hydrogen in the core d) From the motion of convective material What is the semi-major axis of a planet whose period is 11] years? a) 35 AU b) 2.5 AU c) 5AU d) 4.2 AU e) none of the above my answer is : AU A planet has a radius twice the Earth’s radius and a mass twice the Earth’s mass. The planet gravitational force is : a) the same as that of the Earth’s b) twice the Earth’s c) half the Earth’s gravitational force d) one fourth the Earth’s gravitational force e The figure of the on the right shows an HR-diagram in schematic way. Answer the following questions: a) where do you expect the white dwarfs? A B Cc D E b) where do you expect to find a high mass main sequence star? A B Cc D E c) where do you expect to find the subgiants? A B Cc D E e What are the two major greenhouse gases in Earth’s atmosphere? a) O2 and No b) N2 and CO, c}) CO, and CH; d) H20 vapor and CO? P-waves can travel through: a) liquid and solid b) liquid only c) solid only d) neither solid nor liquid Which spectral type has the highest positive color index? a) O-type stars, since they have the highest temperature. b) G-type stars, since they are like the sun. c) Any spectral type, since this is a question of the metallicity of the star. M-type stars, because they have the lowest surface temperature. What caus ‘es a meteor shower? a) Earth crosses the asteroid belt ~~ b) A comet is heated by sunlight Meteor shower is just optical illusion d) Earth crosses the debris littered by a comet. e The graph below a schematic structure of the Milky Way. What number best represent the location of the sun? Answer: 4 eon e Given are the following nuclear reactions: Ro 4 Uy x + = A nSevers : : aed energy -C xX: SO + UN+Y 4 Z 5 Ys e Choose X, Y and Z from the following list: Z : Oo a) ‘He b) tn c) "He d) 8N e) Neutrino ~~ 9) Bo g) Positron ¢ How many protons are consumed in the CNO cycle? a) none b)2 c)4 d)3 e When the chromosphere can be seen during a total solar eclipse, what is its color? a) white b) blue c) green red e) yellow e Ifyou double the radius and the temperature surface of a star, its luminosity increases by a factor of: a) 4 b) 8 c) 16 d) 32 © 4 How many times brighter would a star appear through a 20-cm diameter telescope than through a 10-cm diameter telescope?