If Star A is twice as far as Star B, and they are identical in all other ways, then the brightness of Star A would be
A. the same brightness as Star B.
B. twice the brightness of Star B.
C. one-fourth the brightness of Star B.
D. four times the brightness of Star B.
E. one-half the brightness of Star B.
Answer: C
You might also like to view...
A straight wire is carrying a current upward. Observed from above (i.e., looking downward towards the wire), the magnetic field lines are
A. radially outward. B. radially inward. C. forming clockwise circles. D. forming counter-clockwise circles. E. directed toward the observer.
A section of a composite wall with the dimensions shown below has uniform temperatures of 200°C and 50°C over the left and right surfaces, respectively. If the thermal conductivities of the wall materials are: kA = 70 W/(m K), kB = 60 W/(m K), kc = 40 W/(m K) and kD = 20 W/(m K), determine the rate of heat transfer through this section of the wall and the temperatures at the interfaces.
GIVEN
• A section of a composite wall
• Thermal conductivities
? kA = 70 W/(m K)
? kB = 60 W/(m K)
? kC = 40 W/(m K)
? kD = 20 W/(m K)
• Surface temperatures
? Left side (TAs) = 200°C
? Right side (TDs) = 50°C
FIND
(a) Rate of heat transfer through the wall (q) (b) Temperature at the interfaces
ASSUMPTIONS
• One dimensional conduction
• The system is in steady state
• The contact resistances between the materials is negligible
SKETCH
You hold one end of a solid rod in a fire, and the other end becomes hot. This is an example of __________
Fill in the blank(s) with correct word
A microscope has a tube length of 15.0 cm, an objective focal length of 0.95 cm, and an eyepiece focal length of 2.50 cm. What is the magnification of the microscope? Assume it is adjusted so that the eye is relaxed
a. 122 b. 132 c. 148 d. 12