1. The temperature of stars in the universe varies with the type of star and the age of the star among other things. By looking at the shape of the spectrum of light emitted by a star, we can tell something about its average surface temperature.a. If we observe a star's spectrum and find that the peak power density occurs at the border between red and infrared light, what is the approximate surface temperature of the star? (Remember to include units)Incorrectb. If we observe a star’s spectrum and find that the peak power density occurs at the border between blue and ultraviolet light, what is the surface temperature of the star? (Remember to include units)IncorrectSubmit QuestionQuestion 1 1. The temperature of stars in the universe varies with the type of star and the age of the star among otherthings. By looking at the shape of the spectrum of light emitted by a star, we can tell something about itsaverage surface temperature.a. If we observe a star's spectrum and find that the peak power density occurs at the border betweenred and infrared light, what is the approximate surface temperature of the star? (Remember toinclude units)3715Kb. If we observe a star's spectrum and find that the peak power density occurs at the border betweenblue and ultraviolet light, what is the surface temperature of the star? (Remember to include units)7000 K

We use Weins displacement law, λpeakT=2.838×10-3

1. The temperature of stars in the universe varies with the type of star and the age of the star among other things. By looking at the shape of the spectrum of light emitted by a star, we can tell something about its average surface temperature. a. If we observe a star's spectrum and find that the peak power density occurs at the border between red and infrared light, what is the approximate surface temperature of the star? (Remember to include units) Incorrect b. If we observe a star’s spectrum and find that the peak power density occurs at the border between blue and ultraviolet light, what is the surface temperature of the star? (Remember to include units)

1. The temperature of stars in the universe varies with the type of star and the age of the star among other things. By looking at the shape of the spectrum of light emitted by a star, we can tell something about its average surface temperature. a. If we observe a star's spectrum and find that the peak power density occurs at the border between red and infrared light, what is the approximate surface temperature of the star? (Remember to include units) Incorrect b. If we observe a star’s spectrum and find that the peak power density occurs at the border between blue and ultraviolet light, what is the surface temperature of the star? (Remember to include units)

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter34: Frontiers Of Physics

Section: Chapter Questions

Problem 24CQ: What is critical temperature Tc? Do all materials have a critical temperature? Explain why or why...

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1. The temperature of stars in the universe varies with the type of star and the age of the star among other things. By looking at the shape of the spectrum of light emitted by a star, we can tell something about its average surface temperature. a. If we observe a star's spectrum and find that the peak power density occurs at the border between red and infrared light, what is the approximate surface temperature of the star? (Remember to include units)b. If we observe a star’s spectrum and find that the peak power density occurs at the border between blue and ultraviolet light, what is the surface temperature of the star? (Remember to include units) Submit QuestionQuestion 1
Why don’t we see hydrogen Balmer lines in the spectra of stars with temperatures of 45,000 K? a. There is no hydrogen in stars this hot. b. The stars are hot enough that most of the hydrogen is ionized and the atoms cannot absorb energy. c. These stars are so cool that nearly all of the electrons in the hydrogen atom are in the ground state. d. Stars of this temperature are too cool to produce an absorption spectrum. e. Stars of this temperature are too hot to produce an absorption spectrum.
B2. A spherical star is detected by an astronaut in a spacecraft at a distance z of 1.5×10¹2 kilometers. The star can be regarded as a blackbody with a temperature of 11,300 K. The radius r of the star is 3.5×106 kilometers. (a) Calculate the radiant exitance and the radiant intensity of the star. (b) Calculate the irradiance that can be detected by the astronaut. (c) The photodetector used by the astronaut in the spacecraft has a responsivity of 120 kV/W and an photosensitive area of 0.5 mm². Calculate the output voltage of the detector in the detection of the star. CAMINS +II+ Figure B2
At what wavelength would a star radiate the greatest amount of energy if the star has a surface temperature of 60,000 K? a. 50 nm b. 500 nm c. 300 nm d. 1.8 × 1011 nm e. 180 nm
1. What is the difference between spectral emission and absorption lines? And what is their origin? 2. What is one instance when Boltzmann’s constant appears?
1.1) In a star's core the average mass number for ions which are not hydrogen or helium is 10. The mass fractions of hydrogen is 0.60, of helium is 0.38, and all other elements is 0.02. Calculate the average ion mass in units of mH. 1.2) Explain two assumptions behind the Kelvin-Helmholtz timescale. 1.3) In the outer core of a massive star the temperature is 108 K. The mean particle weight is u = 0.62. Calculate the density of this region if the radiation pressure is equal to the thermal pressure. 1.4) For temperatures around 1.5 x 10' K in a stellar core, describe why it is hydrogen instead of heavier ions which undergo fusion. Also, when the temperature is higher, describe why higher mass ions can undergo fusion. 1.5) Describe two possible causes of convective instability in the outer regions of a low mass star.
Suppose YOUR body temperature averages 98.6 F. 1. How much radiant energy in Wm^-2 is emitted from YOUR body? 2. What is the total radiant energy in W that is emitted from YOUR body? 3. At what wavelength does YOUR body emit the largest amount of radiant energy?
1. Our eyes are most sensitive to light with a wavelength of 550nm. Find the temperature of a black-body radiator whose radiation is most visible to the eye.
19. A hydrogen atom in excited energy state E24x 10" drops down to the ground state at energy level E 21.76 x 10"), giving off a photon. a. What is the energy of the emitted photon injoules? b. What is its wavelength? c. Based on the EM spectrum, what type of raciation is this?
6. What is the temperature of an object if the peak wavelength of its blackbody spectrum is 1200 micrometers? a. 2.4 K b. 25 K С. 322 К d. 833 K e. None of these CS Scanned with CamScanner
2. Can we Estimate the Solar Constant? A result from theoretical physics, known as the Stefan-Boltzmann law, states that the total power radiated by a blackbody at temperature T (K) per unit surface area is given by E=GT* where E is radiated power per unit surface area of the blackbody and o is the Stefan-Boltzmann constant equal to 5.67 x 10* Wm?K*. Let's assume that the sun is a perfect blackbody at T= 5783 K and apply the laws of energy conservation to estimate the average incidence of solar energy [W/m] arriving at the top of Earth's atmosphere (we call that incident energy the solar constant). Compare your calculated estimate of the solar constant to that commonly used to model the sun. Assuming the following constants: d = 1.39e9 m=Diameter of the sun de = 1.27e7 m = Diameter of the earth Res = 1.49el1 m = Mean earth-to-sun distance (HINT: use this distance as the radius of a sphere centered on the sun).
1. Explain the process of excitation, de-excitation, and ionization. 2. What are Lyman, Balmer, and Paschen series of a hydrogen atom? 3. What will be the wavelength of light emitted when in a hydrogen atom an electron jumps from n=5 to n=3 shell? What will be the name of this emission line? What type of telescope/spectroscope (UV, visible, or IR) will you need to observe and record this emission line? 4. You detected a strong Hβ emission line spectrum from your source toward the center of the Milky Way. What can you tell about the nature of the radiation source? 5. An electron in an excited state falls to the ground state by interaction with a free electron. Write the equation to represent this process. Will any photon be emitted in this case? Why or why not? 6. What is optical depth? What happens if a medium is optically think? Optically thin? 7. Using the radiative transfer equation of a simple slab-like absorbing medium with no internal emission source, I = I0 exp(−n σ x), where I0…