Some material from meteors lingers in the mesosphere, causing this layer to have a relatively high concentration of iron and other metal atoms. Very strange, high altitude clouds called "noctilucent clouds" or "polar mesospheric clouds" sometime form in the mesosphere near the poles.
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Answer:
D. If the distance between the crests of the waves increase, the frequency decreases.
Explanation:
Wavelength is the distance between two successive crests and troughs while frequency is the number of complete cycle per seconds
Velocity = Frequency × wavelength
Frequency and wavelength are inversely proportion
We know,
PV=nRT
203*20= n*0.0821*373
n=132.5 moles.
Answer:

Explanation:
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In this case, it possible to use the Rydberg equation in order to calculate the wavelength for this transition from n=3 to n=2 as shown below:

Thus, we plug in the corresponding energy levels and the Rydberg constant to obtain:

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The notation is actually written in this way (shown in the attached picture). The X is the symbol of the element. So, for potassium, the symbol is K. The A represents the mass number of the isotope. In this case, that would be equal to 39. The Z represents the atomic number of potassium, which is 19. Therefore, the symbol for the isotope is:
³⁹₁₉K