Increasing the focal length in a telephoto lens by a factor of nine, while keeping the aperture size constant, will change the f-number by what factor?
a. 1/3
c. 9
b. 1/9
d. 3
C
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Which of the following models best explains why our galaxy has spiral arms?
A) The spiral arms are a wave of star formation caused by a wave of density propagating outward through the disk of the galaxy. B) The spiral arms are composed of groups of stars that are bound together by gravity and therefore always stay together as the galaxy rotates. C) The spiral arms were imprinted on the galaxy at its birth. Ever since, like a coiling rope, the spiral arms have been wound tighter with each galactic rotation. D) No model can explain the existence of the arms, which rotate with the galaxy like the fins of a giant pinwheel toy.
A tropical year is the same as a sidereal year
Indicate whether the statement is true or false
A solid block of metal in electrostatic equilibrium is placed in a uniform electric field. Give a statement concerning the electric field in the block's interior
A) The interior field points in a direction opposite to the exterior field. B) The interior field points in a direction that is at right angles to the exterior field. C) The interior points in a direction that is parallel to the exterior field. D) There is no electric field in the block's interior. E) Not enough information is given to make a statement concerning the elecric field on the block's interior.
Compounds tend to be ______________ compounds if they are formed from two or more nonmetals
a. covalent b. organic c. polar d. ionic