A magician can make a candle look as if it is burning under water by focusing light from a candle flame burning in air directly on top of an underwater candle. To do this you want to use a (Hint: eliminate those that cannot work.)
a. concave mirror farther than one focal length from the burning candle.
b. a convex mirror farther than one focal length from the burning candle.
c. a biconcave lens farther than one focal length from the burning candle.
d. a concave mirror closer than one focal length to the burning candle.
e. a convex lens closer than one focal length to the burning candle.
a
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Compound Microscope: The focal lengths of the objective lens and the eyepiece of a microscope are 0.50 cm and 2.0 cm, respectively, and their separation adjusted for minimum eyestrain is 6.0 cm. If the microscope is focused on a small object, what is the distance between the object and the objective lens?
A. 0.31 cm B. 0.42 cm C. 0.49 cm D. 0.57 cm E. 0.73 cm
The Local Bubble was probably created by:
A) the strong solar winds created by the new-born Sun. B) the Crab Nebula supernova of 1054 AD. C) the magnetic fields of the Milky Way in our spiral arm. D) a nearby supernova perhaps 300,000 years ago, brighter than the full Moon. E) the interaction between the solar wind and the Oort Cloud.
Which of the following statements is correct?
a. You only need to know the amount of thermal energy a body contains to calculate its temperature. b. The temperature of a body is directly proportional to the amount of work the body has performed. c. The quantity of thermal energy exchanged by two bodies in contact is inversely proportional to the difference in their temperatures. d. The quantity of thermal energy exchanged by two bodies in contact is directly proportional to the difference in their temperatures. e. Different amounts of thermal energy are transferred between two bodies in contact if different temperature scales are used to measure the temperature difference between the bodies.
In a region of space where the electric field is radial, suppose that Er = C/r3, where C is a positive constant. Is the charge density ? in this region positive, negative, or zero? (Note: ? might depend on r in this region.)
A. Positive B. Negative C. Zero D. This is impossible.