Luminosity has units of energy per time. Apparent brightness has units of energy per time per area. Which of the following expressions correctly states the relationship between luminosity, distance, and apparent brightness (known as the "inverse square law for light")?
A) luminosity =
B) apparent brightness =
C) apparent brightness = luminosity × 4? × (distance)2
D) distance =
B) apparent brightness =
You might also like to view...
For most materials, the fatigue endurance limit is what percentage of the yield stress?
(a) 60 to 80 (b) 35 to 60 (c) 25 to 35 (d) 15 to 25
The hot gas of the big bang seems to be cool at about 2.7 K because:
A) the expansion of the Universe has decreased the wavelengths of the radiation emitted by the big bang. B) the gas clouds that emitted the photons during the big bang had a temperature of 2.7 K. C) the expansion of the Universe has redshifted the wavelengths of the radiation emitted by the big bang about 1100 times longer. D) the gas clouds that emitted the photons during the big bang emitted blackbody radiation with a wavelength of 2.7 nm.
Thin Lenses: A cell phone is placed 40 cm in front of a converging lens with a focal length of magnitude 20 cm. How far is the image of this phone from the lens?
A. 40 cm B. 20 cm C. 13 cm D. 60 cm E. 10 cm
A conducting rod (length = 80 cm) rotates at a constant angular rate of 15 revolutions per second about a pivot at one end. A uniform field (B = 60 mT) is directed perpendicularly to the plane of rotation. What is the magnitude of the emf induced between the ends of the rod?
A. 2.7 V B. 2.1 V C. 2.4 V D. 1.8 V E. 3.3 V