The Sloan Digital Sky Survey includes many thousands of galaxies in its spectroscopic catalogs. How are the distances to most of these galaxies estimated?
A) from their redshifts and the application of Hubble's Law
B) by measuring Cepheid variable light curves
C) by measuring their parallax angle as the Earth circles the Sun
D) by measuring the light from white dwarf supernovae
A) from their redshifts and the application of Hubble's Law
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A car travels a distance of 100 km. For the first 30 minutes it is driven at a constant speed of 80 km/hr. The motor begins to vibrate and the driver reduces the speed to 40 km/hr for the rest of the trip. The average speed for the entire trip is
A. 50.0 km/hr. B. 60.0 km/hr. C. 53.3 km/hr. D. 47.5 km/hr. E. 40.0 km/hr.
A beam of white light in air passes through the transparent object shown. Dispersion is observed to occur. From the diagram we can tell that
A. the object behaves as a concave mirror. B. the object acts as a converging lens. C. the index of refraction is larger for blue light than red. D. the index of refraction is larger for red light than blue.
Thermal Expansion: The coefficient of linear expansion of copper is 17 × 10-6 K-1. A sheet of copper has a round hole with a radius of 3.0 m cut out of it. If the sheet is heated and undergoes a change in temperature of 80 K, what is the change in the radius of the hole?
A. It decreases by 4.1 mm. B. It increases by 4.1 mm. C. It decreases by 8.2 mm. D. It increases by 8.2 mm. E. It does not change.
A radioactive isotope that emits an alpha particle will change in what respect?
a. Atomic number decreases by four. b. Mass number decreases by four. c. Both choices a and b are valid. d. None of the above choices are valid.