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Unformatted text preview: £5? 393.8
HGMEWORK #6
QUE 11f3lli ALL 0? THESE PRGBLEMS ARﬁ FROM THE TEX? 2.3) The apparent magnitude of the Sun is —26.8. How much brighter does the Sun
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WWWW “30:3 «— e eat; 2.26) (a) if we can measure parallaxes as small as 0.1 arc sec, what is the greatest
distance that can be measured using the method of trigonometric parallaxes? (b) By
what factor will the volume of space over which we can measure parallax change if we
can measure to 0.001 arc sec? (c) Why is the volume of space important? ‘9’) {330A Oll'w’l" :1 “L, x {(3 53¢. 55 {A :o,eo; algaA" M “M 3; {maﬁa 3 1
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”3 {£le 3 ﬂ 3L “3:: reﬁll/f" Oi :; moral fl 4.7) The focal length of the objective on your telescope is 0.5 m. (a) What focal
length eyepiece would you have to use to have the image ofthe full Moon (whose
actual size is 30 arc min) subtend an angle of 2 degrees? (b) If you then took a photograph with a 500 mm focal length camera lens, how large would the image be
on the film? A) [44 3&0 .3. a {$2, I: 2;”
’““ {3; (E). "““ {9 i) 4.13) Suppose you have a Cassegrain telescope at home, with a 0.25 m diameter primary mirror and a secondary mirror with a diameter of 5 cm. What fraction of
the primary is blocked by the secondary? 3f Camus” ”it 4.29) If a radio source emits a solar luminosity (4x1033 erg/s) in radio waves, (a)
What would be the power per surface area reaching us if we ‘were (i) 1 AU away, (ii) 1 pc away? (b) Ifthat power is uniformly spread out over a frequency range of
1011 Hz, what is the flux density (power/surface area/Hz) in each case? (c) How does
this compare with the power you receive from a 50 kW radio station 10 km from you? :53 IQ: Li'XI’DE: :ezg/ggg
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63 gas Keﬂ’ﬁ m am. “age ‘ Wit»; 2? We m £3 w 4.32) What is the total collecting area of (a) the VLA (b) the ALMA with 75 10 m
diameter telescopes? (c) For ALMA, how many 12 m diameter telescopes would you
need to have the same collecting area as 75 10 m diameter telescopes? a) WA: 4'? " Team? :5: ﬁﬁfamaf ZJQWJM 53347 i L 2.3” I 2”?
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 Fall '08
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