Segmented mirrors sag under their own weight. Their optical shape must be controlled by computer-driven thrusters under the mirrors in what is called
a. an achromatic lens.
b. active optics.
c. a Schmidt-Cassegrain design.
d. a Newtonian design.
e. interferometry.
B
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Globular clusters can be used to measure the distance of nearby galaxies
a. True b. False Indicate whether the statement is true or false
A transverse periodic wave is represented by the equation y(x, t) = -1.50 cm sin(1,500 rad/s t - 10.0
x). Another transverse wave is represented by the equation y(x, t) = +1.50 cm sin(1,500 rad/s t + 10.0
x). What is the equation that represents the superposition of the two waves?
A. y(x, t) = 3.0 cm sin(1,500 rad/s t - 10.0
x)
B. y(x, t) = 3.0 cm sin(1,500 rad/s t) cos(10.0x)
C. y(x, t) = +3.0 cm cos(1,500 rad/s t) sin(10.0x)
D. y(x, t) = 3.0 cm sin(1,500 rad/s t + 10.0x)
A 140 gm baseball with a velocity of 25.0 m/s is hit by a baseball bat and leaves at 30.0 m/s in the opposite direction. If the ball was in contact with the bat for 12.0 ms, what is the average force on the ball?
A. 750 N B. 642 N C. 550 N D. 482 N E. 366 N
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.