Radio waves are produced by
A) nuclear vibrations.
B) molecules in thermal motion.
C) electrons orbiting around the nucleus in atoms.
D) electric currents oscillating in human-made electronic devices.
E) mechanical oscillators that move air back and forth.
D
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The helium flash converts helium into ________
Fill in the blank(s) with correct word
A candle emits what kind of spectrum?
A. blueshifted B. emission-line C. absorption-line D. continuous E. redshifted
Spiral arms are thought to be sites of ________, based on the observations newly formed stars and interstellar dust lanes in and around these features
Fill in the blank(s) with correct word
The quantity "pressure" expressed in terms of the fundamental quantities (mass, length, time) is equivalent to:
a. MLT-1. c. M2L-1T-3. b. ML-1T-2. d. a dimensionless quantity.