Why are most large telescopes reflectors, not refractors?
A) Large lenses deform under their own weight, but mirrors can be supported.
B) Large mirrors need only one optical surface, achromats four surfaces to grind.
C) Reflectors do not suffer from chromatic aberration like refractors do.
D) Large, very clear lenses are harder to cast than more tolerant mirror blanks.
E) All of the above are correct.
E
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The thermal pressure within a gas depends on
A) density only. B) temperature only. C) density and temperature. D) composition. E) gravity.
A stretched string is observed to vibrate in three equal segments when driven by a 480-Hz oscillator. What is the fundamental frequency of vibration for this string?
a. 480 Hz b. 320 Hz c. 160 Hz d. 640 Hz e. 240 Hz
Satellite Motion: Suppose NASA wants a satellite to revolve around Earth 5 times a day. What should be the radius of its orbit if we neglect the presence of the Moon? (G = 6.67 × 10-11 N ? m2/kg2, Mearth = 5.97 × 1024 kg)
A. 1.44 × 107 m B. 0.69 × 107 m C. 7.22 × 107 m D. 2.11 × 107 m