A surveyor wishes to measure the distance between two points on either side of a river, as illustrated in the figure. She measures the distance AB to be 230 m and the angle at B to be 20°. What is the distance between the two points?

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1 m

Using the data in the table, estimate the minimum possible distance between Mercury and Earth.

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1 AU

If Earth were completely blanketed with clouds and we couldn't see the sky, could we learn about the realm beyond the clouds?
1

What forms of radiation might be received? (Select all that apply.)

Calculate the wavelength and frequency of the radiation emitted by the electronic transition from the tenth to the ninth excited state of hydrogen.
wavelength

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1 µm
frequency

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2 MHz
In what part of the electromagnetic spectrum does this radiation lie?


Repeat the question for transitions from the 100^th to the 99^th excited state.
wavelength

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4 cm
frequency

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5 MHz
In what part of the electromagnetic spectrum does this radiation lie?


Repeat the question for transitions from the 1000^th to the 999^th excited state.
wavelength

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7 m
frequency

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8 MHz
In what part of the electromagnetic spectrum does this radiation lie?

Based on collecting areas, how much more sensitive would you expect the Arecibo telescope (diameter = 300 m, Figure A) to be, compared with the large telescope in Figure B (diameter = 105 m)?

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1

Which planets have been visited by spacecraft from Earth? (Select all that apply.)

On which ones have spacecraft actually landed?