Radio waves travel at the speed of light, 300,000 km/s. The wavelength of a radio wave received at 100 megahertz is
A) 0.3 m.
B) 3.0 m.
C) 30 m.
D) 300 m.
E) none of the above
Answer: B
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In the context of life in the universe, which of the following discoveries of astronomy suggests that extraterrestrial life may be constructed in a similar fashion to life on Earth?
A) the universe is very large B) the universe is very old C) the laws of physics are the same everywhere D) the chemical elements that make up life on Earth are common
The large space telescope that has been placed into an Earth orbit has an aperture diameter of 2.40 meters. What angular resolution will this telescope achieve for visible light of wavelength ? = 4.80 × 10^?7 m?
a. 2.44 × 10^?7 rads b. 2.44 × 10^?4 rads c. 2.44 × 10^?3 rads d. 1.22 × 10^?6 rads e. 2.00 × 10^?6 rads
An alloy of 80 atomic % arsenic and 20 atomic % gallium is produced, and the alloy is heated to 1250°C to thoroughly melt the mixture. The alloy is then slowly cooled so that it is always close to equilibrium. Answer the following about the alloy:
(a) At what temperature does a solid first form?
(b) What is the chemical composition of the first solid to form?
(c) Below what temperature is the alloy completely solid?
(d) At room temperature (23°C), what phases are present, what are their chemical compositions, and what is the atom fraction of each phase present?
A 0.30-kg block of wood is suspended on a spring. In equilibrium the wood stretches the spring 2.0 cm downward. The wood is then pulled an additional distance of 1.0 cm down and released from rest
(a) How long does it take the wood to make 3 complete cycles of vibration? (b) How much total mechanical energy does this system contain if we choose the total potential energy (elastic and gravitational) to be zero at the equilibrium position of the hanging block?