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weeeeeb [17]
3 years ago
7

An astronomy class is so excited by the discovery of planets around other stars that they decide to do a library exhibit on the

subject so that everyone in the school can learn about it. In this exhibit they want to pay tribute to both the astronomers of today who have done the work AND some of the scientists of the past whose work was essential to making the discoveries possible (and directly related to the techniques involved). Which of the following scientists of the past should definitely be included in the exhibit?
a. George Herbigâ
b. Ejnar Hertzsprungâ
c. Ptolemyâ
d. Gerard Kuiperâ
e. Christian Dopplerâ
Physics
1 answer:
tekilochka [14]3 years ago
8 0

Answer: e. Christian Dopplerâ

Explanation:

Based on the information given, the scientist of the past that should definitely be included in the exhibit is Christian Dopplera.

He described how the frequency of sound waves and light is being affected by the relative speed of both the source and also the observer. This was referred to as the Doppler effect.

In this scenario, the Doppler effect can be used to show how the universe is expanding. Therefore, the correct option is E.

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6 0
3 years ago
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Bezzdna [24]
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5 0
4 years ago
We can reasonably model a 90-W incandescent lightbulb as a sphere 5.7 cm in diameter. Typically, only about 5% of the energy goe
o-na [289]

Answer:

See answer

Explanation:

Given quantities:

\eta = 0.05\\ W=90[W]\\r=0.0285[m]

where \eta is the efficiency of the lightbulb (visible light is 5% of the total power), W is the total power of the lightbulb, r is the radius of the lightbulb in meters.

Intensity is power divided by area:

I =\frac{P}{A}

a) Now the effective power is \eta*W, therefore:

I =\frac{\eta*W}{\pi r^2}=\frac{0.05*90}{4\pi (0.0285)^2}=440.87[W/m^2]

b) Now the intensity is the average poynting vector is related to the magnitudes of the  maximum electric field and magnetic field amplitudes, following:

S_{average}= \frac{EB}{2\mu_{0}}[W/m]

now E and B are related:

E=cB\\ B=\frac{E}{c} and c=\frac{1}{\sqrt{\epsilon_{0} \mu_{0}}}

replace in S_{average}

S_{average}=I= \frac{c \epsilon_{0}E^2}{2}[W/m]

we replace the values and we get:

E= \sqrt{\frac{2I}{\epsilon_{0}c}}

E = \sqrt{\frac{2(440.8)}{8.85*10^{-12}3*10^8}}=576.24[V/m]

therefore

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8 0
3 years ago
If a wave has a period of 0.5 s, what is its frequency
Naddik [55]
Frequency is 1/period.  f=1/0.5 = 2Hz
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3 years ago
10 points
JulijaS [17]

Answer:

I think the answer might be the 2nd one or 3rd one.

8 0
3 years ago
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