Tan's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and upright, what is the focal length of the mirror?
A) 10 cm
B) -40 cm
C) -50 cm
D) 40 cm
E) 50 cm
D
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A heavy downpour associated with a severe local storm is commonly referred to as
a) a rainstorm. b) a blizzard. c) a shower. d) an electrical storm.
Igneous rock is formed from
A) crystallization of molten magma. B) high temperatures and pressures. C) solidified lava beneath the Earth's surface. D) any of these
When we add a displacement vector to another displacement vector, the result is:
a. a velocity. c. another displacement. b. an acceleration. d. a scalar.
The tungsten filament of a light bulb has an operating temperature of about 2100 K. If the emitting area of the filament is 0.80 cm2, and its emissivity is 0.68, what is the power output of the light bulb? (s = 5.67 × 10^-8 W/m2 • K4)
a. 100 W c. 60 W b. 75 W d. 40 W