Discuss the solution to the flatness problem and horizon problem of the Universe
What will be an ideal response?
The key to the flatness problem and the horizon problem and to other problems with the simple big bang model may lie with a modified model called the inflationary big bang that predicts there was a sudden extra expansion when the Universe was very young, even more extreme than that predicted by the original big bang model. According to the inflationary Universe model, the Universe expanded and cooled until about 10-36seconds after the big bang. Then, the Universe became cool enough that the forces of nature, which at earlier extremely high temperatures would have behaved identically, began to differ from each other. Physicists calculate this would have released tremendous amounts of energy and suddenly inflated the Universe by a factor of 1050or larger. As a result, the part of the Universe that is now visible from Earth, the entire observable Universe, expanded rapidly from 1035times smaller than a proton to roughly a meter across and then continued a slower expansion to its present state.That sudden inflation can solve both the flatness problem and the horizon problem. The inflation of the Universe would have forced whatever curvature it had toward zero, just as inflating a balloon makes a small spot on its surface flatter. You now live in a Universe that has almost perfectly flat space-time geometry because of that sudden inflation long ago. In addition, because the observable part of the Universe was no larger in volume than an atom before inflation, it was small enough to have equalized its temperature by then. Now you live in a Universe that has the same cosmic microwave background temperature in all directions.
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Matter Waves: A crystal diffracts a beam of electrons, like a diffraction grating, as they hit it perpendicular to its surface. The crystal spacing is 0.18 nm, and the first maximum scattering occurs at 80° relative to the normal to the surface. (e = 1.60 × 10-19 C, melectron = 9.11 × 10-13 kg, h = 6.626 × 10-34 J ? s)(a) What is the wavelength of the electrons?(b) What potential difference accelerated the electrons if they started from rest?
Fill in the blank(s) with the appropriate word(s).
Briefly explain how we can use spectral lines to determine an object's radial motion. Can we also learn the object's tangential motion (across our line of sight) from its spectral lines?
What will be an ideal response?
If n1 is the index of refraction for the incident medium and n2 is the index for the refracting medium, the critical angle will exist
A) in all cases, it will just have different values. B) when n1 < n2. C) when n1 = n2. D) never. E) when n1 > n2.
If an electron is accelerated from rest through a potential difference of 25,000 volts in a color television picture tube, its kinetic energy will be
A) 16 J. B) 2.5 × 104 J. C) 4.0 × 10-5J. D) 1.6 J. E) 4.0 × 10-15 J.