When observing the Sun in visible light, the photosphere appears brighter than the corona. However, when observing the Sun in x-rays, the corona appears brighter. The reason for this is that
A. the gas in the corona has a much lower density than that in the photosphere and so emits mostly emission lines at x-ray wavelengths.
B. the temperature in the corona is more than 1 million K while that in the photosphere is about 5800 K and so the corona emits a larger fraction of its luminosity at short wavelengths.
C. more nuclear reactions are occurring in the corona than the photosphere and these produce high-energy (x-ray and gamma-ray) photons.
Ans: B. the temperature in the corona is more than 1 million K while that in the photosphere is about 5800 K and so the corona emits a larger fraction of its luminosity at short wavelengths.
There is much more gas in the photosphere than in the corona (the gas is denser in the photosphere), so the photosphere emits more total energy in electromagnetic radiation. However, the much higher temperature of the corona compared to the photosphere shifts the peak of its thermal emission to much shorter wavelengths (i.e., from visible light to x-rays). The result is that the photosphere is brighter near the peak of its emission (visible wavelengths), but the corona is brighter near its peak (x-rays). It is true that low-density gas tends to produce an emission-line spectrum, but the lines need not be at x-ray wavelengths. Finally, there are no nuclear reactions occurring in the photosphere or corona of the Sun (they only occur near the center).
You might also like to view...
Two stars have the same spectral type. Star X is in luminosity class III, while Star Y is in luminosity class V. Therefore, Star X is larger in radius than Star Y
Indicate whether the statement is true or false
We determine the structure of the Earth's core using
A) deep mine shafts. B) satellite imaging. C) radar and sonar. D) seismic wave data. E) magnetic resonance imaging.
If a planet has a radius 16.0% greater than that of the Earth but has the same mass as the Earth, what is the acceleration due to gravity at its surface?
a. 8.45 m/s2 b. 1.57 m/s2 c. 10.0 m/s2 d. 7.28 m/s2
A solid steel sphere with a radius of 2.0 m falls off a ship and sinks to a depth where the pressure is 15 MN/m2. The bulk modulus for this steel is 1.6 × 1011 N/m2. What is the change in the radius of the sphere?
A) -0.021 mm B) -4.2 mm C) -0.42 mm D) -0.19 mm E) -0.062 mm