How can interstellar dust block starlight in spite of its extremely low density?
What will be an ideal response?
The grain size of the dust is comparable to the wavelength of the light blocked, so scattering of light is possible. Also, clouds are so vast that even at low density they contain a lot of dust.
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Which is smallest, an atom, a nucleus, a proton, or an electron?
a. atom b. electron c. nucleus d. proton
Three identical capacitors are connected in series across a potential source (battery). If a charge of Q flows into this combination of capacitors, how much charge does each capacitor carry?
A) 3Q B) Q C) Q/3 D) Q/9
Which of the following is not an observed characteristic of the cosmic microwave background?
A) It contains prominent spectral lines of hydrogen, the primary chemical ingredient of the universe. B) It has a perfect thermal radiation spectrum. C) Its temperature is the same everywhere, except for small variations at the level of 1 part in 100,000. D) Its temperature is a little less than 3 Kelvin (3 degrees above absolute zero).
Consider a submarine at a depth of 67. meters in sea water (density 1.03 grams/cc) and the interior of the sub is at 1.0 atmosphere
(a) What is the outside pressure at that depth? (b) Find the total force that must be withstood by a square hatch (0.90 m square) which leads to the sub interior.