The concentration of oxygen in the atmosphere has been near or above its current value for the past
A) 200 million years
B) 542 million years
C) 65 million years
D) 360 million years
A
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Olbers' paradox asks
A. Why isn't the night sky bright as day? B. How can the Universe be younger than some of the stars in it? C. If dark matter is dark, how can we ever see it? D. Which is the simplest cosmological model?
If you find you are able to move a positive charge from infinity (far away) to a particular point without doing any work, can you infer that no other charges are nearby?
What will be an ideal response?
Light of wavelength 633 nm from a He-Ne laser passes through a circular aperture and is observed on a screen 4.0 m behind the aperture. The diameter of the central bright area is 5.4 cm. What is the diameter of the aperture?
A) 2.0 ?m B) 960 ?m C) 110 ?m D) 6600 ?m
The number of cycles of a periodic process that occur per unit time is called the __________
Fill in the blank(s) with correct word