What observations indicate the presence of dust in the interstellar medium?
What will be an ideal response?
The dust in the ISM makes distant stars appear fainter than they would if space were
perfectly transparent. This phenomenon is called interstellar extinction, and in the neighborhood of the Sun it amounts to about 1 magnitude per thousand parsecs (pc) at visual wavelengths.
The ISM dust also affects the colors of stars. That is the reason why extinction is more severe at shorter wavelengths, which makes stars look redder than they should be. Some hot but distant O stars, for instance, actually look red and not blue. This effect is called interstellar reddening.
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Two tuning forks have frequencies of 440 and 522 Hz. What is the beat frequency if both are sounding simultaneously?
A) 962 Hz B) 481 Hz C) 82 Hz D) 55 Hz E) 41 Hz
The theory of continental drift is attributed to
A) H.H. Hess. B) Alfred Wegener. C) W. Loma Prieta. D) Simon Tectonic.
A spherical surface surrounds a point charge it its center. If the charge is doubled and if the radius of the surface is also doubled, what happens to the electric flux ?E out of the surface and the magnitude E of the electric field at the surface as a result of these doublings?
a. ?E and E do not change. b. ?E increases and E remains the same. c. ?E increases and E decreases. d. ?E increases and E increases.
When a molecule collides with another that is approaching with greater momentum, its rebound speed
1) stays the same, 2) increases, 3) decreases, and when a molecule collides with another that is receding, its rebound speed 4) stays the same. 5) increases. 6) decreases.