The answer is B. metalloids
(boron, silicon, germanium, arsenic, antimony, tellurium, astatine, and polonium)
This is a Doppler effect. Generally, if you move to a frequency source, you would detect an increase in frequency and when you move away from a source you would detect a decrease.
For this question, before you pass them, you are actually approaching them, so you would hear a higher frequency than the constant 300 Hz they are playing at.
Using the condensed formula:
f ' = ((v <u>+</u> vd)/(v <u>+</u> vs)) * f
Where: vd = Velocity of the detector.
vs = Velocity of the frequency source.
v = Velocity of sound in air.
f ' = Apparent frequency.
f = Frequency of source.
v = 343 m/s, vd = detector = 27.8 m/s, vs = velocity of the source =0. (the flautists are not moving).
f = 300 Hz.
There would be an overall increase in frequency, so we maintain a plus at the numerator and a minus at the denominator.
f ' = ((v + vd)/(v - vs)) * f
f ' = ((343+ 27.8)/(343 - 0)) * 300
= (370.8/343)* 300 = 324.3
Therefore frequency before passing them = 324.3 Hz.
Cheers.
The surface temperature of a red star is lower than the surface temperature of a yellow star.
Explanation:
For a red star, the peak of the wavelength of the emitted light is in the red spectrum, therefore the average peak wavelength is:
The corresponding temperature at the surface of the star can be found by using Wien's displacement law:
where
is a constant. Substituting, we find
For a yellow star, the peak of the wavelength of the emitted light is in the yellow spectrum, therefore the average peak wavelength is:
So we can use again the same equation to find the corresponding surface temperature of a yellow star:
Therefore, we see that the surface temperature of a red star is lower than the surface temperature of a yellow star.
Learn more about temperature:
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