Which of the following terms describe lenses that are thicker at the center than at the edges? (There could be more than one correct choice.)
A) converging lenses
B) diverging lenses
C) concave lenses
D) convex lenses
A, D
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On the H-R diagram, white dwarfs lie Sirius B and Procyon B lie
A) at the top left. B) at the top right. C) close to the Sun, near the center. D) at the lower left. E) at the lower right.
The light-year is defined to be the
A) time it takes light to travel from the Sun to the Earth B) time it takes for light to travel from the nearest star to the Earth C) distance light travels in one year in space D) average distance between the Earth and the nearest star
A supersonic plane passes overhead at a speed of 500 m/s. If you hear the sonic boom (shock wave) 4.00 s after the plane is directly overhead, at what altitude is the plane flying? Assume the speed of sound in air is 340 m/s
A) 1.36 km B) 2.16 km C) 1.85 km D) 2.45 km E) The plane is not flying fast enough to produce a shock wave.
Four of following are factors that must be overcome by a large molecular cloud before gravitational contraction can begin. Which one is the exception??
A. thermal energy of gas B. magnetic fields C. rotation of gas clouds D. intense radiation from a nearby star