What is the wavelength of the photon emitted when an electron in a hydrogen atom which is in the initial state n = 4 jumps to the final state n = 2? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J)
A) 243 nm
B) 486 nm
C) 556 nm
D) 312 nm
E) 609 nm
B
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An annular solar eclipse occurs
A. when the Moon in its orbit is closest to Earth, and, so not able to cover the complete disk of the Sun. B. every year when the Sun is highest in the sky. C. when the Moon in its orbit is farthest from Earth, and, so not able to cover the complete disk of the Sun. D. None of these choices is correct.
If the efficiency of a reversible engine is 28.%,
(a) what is its COP operated as a refrigerator? (b) what is its COP operated as a heat pump?
Tycho Brahe's extremely accurate measurements of the planetary positions showed that
A) Kepler's theory was wrong. B) both Ptolemy's theory and Copernicus's theory were correct. C) both Ptolemy's theory and Copernicus's theory were wrong. D) Copernicus's theory was wrong and Ptolemy's was correct. E) Ptolemy's theory was wrong and Copernicus's theory was correct.
Damage from an earthquake is most severe when the
A) epicenter is close to the surface. B) surface material is composed of unconsolidated sediments. C) buildings and structures are poorly constructed. D) all of the above