Why does the Cepheid "standard candle" have limited usefulness beyond 20 Mpc?
A) Distant galaxies are seen in the past, when Cepheid variables behaved differently than they do today.
B) Distant galaxies are so young they do not contain Cepheids.
C) Cepheids are too faint to be seen beyond that distance, even with HST.
D) The light variability of Cepheids diminishes with distance so they do not appear to vary there.
E) Older distant Cepheids are of Population II, where the period-luminosity relation no longer works.
C
You might also like to view...
A system consists of two photons moving in opposite directions. One photon has energy E and the other has energy 4E. The total system’s mass M is
A. Zero, of course. B. 3E. C. 4E. D. 5E. E. Something else (specify).
In choosing between sound waves and radio waves, which has the greater speed?
A) sound wave B) radio wave C) both the same D) need more information
A satellite circles planet Roton every 2.8 h in an orbit having a radius of 1.2 × 107 m. If the radius of Roton is 5.0 × 106 m, what is the magnitude of the free-fall acceleration on the surface of Roton?
A. 31 m/s2 B. 27 m/s2 C. 34 m/s2 D. 40 m/s2 E. 19 m/s2
A ray of light travels from a glass-to-liquid interface at an angle of 41.8°. Indices of refraction for the glass and liquid are, respectively, 1.52 and 1.63 . What is the angle of refraction for the ray moving through the liquid?
a. 23.2° c. 32.3° b. 46.0° d. 38.4°