Philosophy 2203E Chapter : Certain Truths.docx

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rubydinosaur559

18 Jul 2012

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There is nothing more commonly taken for granted than that there are certain principles both speculative and practical universally agreed upon by all mankind. Must bends to be the constant impressions, as they do any of their inherent faculties. That if it were true in matter of fact that there were certain truths wherein all mankind agreed, t would not prove them innate. Argument of universal consent which is made use of to prove innate principles, so settled a reputation of maxims universally received. Be though strange if anyone should seem to question it, propositions are so far from having any universal assent a great part of mankind. All children and idiots have no the least apprehension or thought of them universal assent needs to be necessary concomitant of all innate truths. Therefore children and idiots have souls, have minds with those impressions upon them they must unavoidably perceive them, and necessarily know and asset to these truths.

Related Questions

A Particle in a box
In order to answer the following questions you will need toconsideran infinite potential
well of length L, in which a particle has been confined.

1. For principal quantum number n=7, write code to calculatethenormalization constant.
Then, plot the probability density function for this state (usingL= 10).
2. Using the properly normalized wave equation from Question1,write code to determine
the expectation values <x> and <x2> . Is <x>oneof the most probable positions? Explain
why.
3. Using the properly normalized wave equation from Question1,write code to determine
the expectation values <p> and <p2> . Show the valueyouobtain for <p2> is equal to
2mE7 (where E7 is the energy of the n = 7 level). Remember that pisa differential
operator so you will have to use the diff command.
4. The uncertainty of a quantum measurement is defined on page222,Equation 6.41 (3rd
edition SMM). Using this equation calculate the uncertainties oftheposition and
momentum of a particle in the n = 5 state. Compute the productofthese uncertainties and
compare this with the prediction of the Heisenberguncertaintyprinciple.
Quantum oscillator
5. Repeat calculations in the previous question for the groundstatewave function of the
quantum oscillator. Comment on the obtained result.

3. a) Show that the phase velocity of the de Broglie waves of aparticle of mass m and de Broglie wavelength ? is given by .
b) Compare the phase and group velocities of an electron whose deBroglie wavelength is exactly 1x10-13 m.
4. To what voltages must we accelerate electrons (as in an electronmicroscope, for example) if we wish to resolve;
a) a virus of diameter 12 nm , b) an atom of 0.12 nm, c) a protonof diameter 1.2 fm?
5. a) The x-coordinate of an electron is measured with anuncertainty of 0.20 mm. What is the x- component of the electronâsvelocity, vx, if the minimum percentage uncertainty in asimultaneous measurement of vx is 1.0%.
b) Repeat part (a) for a proton. 6. Suppose Fuzzy, a quantummechanical duck, lives in a world in which h = 2? J.s. Fuzzy has amass
of 2.0 kg and is initially known to be within a region 1.0 mwide.
a) What is the minimum uncertainty in his speed? b) Assuming thisuncertainty in speed to prevail for 5.0 s, determine theuncertainty in position after
this time.
7. The seeing ability, or resolution, of radiation is determined byits wavelength. If size of an atom is of the order of 0.1 nm, howfast must an electron travel to have a wavelength small enough toâseeâ an atom?
8. An air rifle is used to shoot 1.0 g particles at 100 m/s througha hole of diameter 2.0 mm. How far from the rifle must an observerbe to see the beam spread by 1.0 cm because of the uncertaintyprinciple? Compare this answer with the diameter of the universe (? 1026 m).

Huygens' principle (first described by the Dutch scientist Christiaan Huygens in 1678) uses geometry to determine the shape of a wavefront at a time t, given some initial wavefront at an earlier time. This can be constructed by imagining that the initial wavefront is a source of wavelets that propagate from each point at the speed of light. From this principle, one can determine the angles of reflection and refraction by considering the speed of light at each point on the wavefront. In this problem, we will explore some of these concepts.

Part A

First, let's look at a plane wave that is incident on a flat piece of material with an index of refraction n. Part of the light is transmitted through the material and part of it is reflected. For the moment, let's just look at the part that is transmitted. At time t=0, the wavefront is a distance d away from the surface of the material. At time t=t₁, the wavefront is at the position of the material interface. Use the Huygens' principle to determine how far into the material (d') the wavefront has propagated by time t=2t₁.

Express your answer in terms of the variables n, t₁, and the speed of light in a vacuum c.

Note that there would be no change in the direction of the wavefront at any point because the wavefront encountered the material interface at the same time at all points. Thus, all of the individual wavefronts all propagated at the same speed, thereby maintaining the flat wavefront.

Now, instead of having a flat wavefront propagating normal to the material interface, we have a flat wavefront propagating toward the material at an angle of 55° to the axis perpendicular to the material interface. In this part, we will look at the relative positions of a few points—A, B, and C—on the wavefront to illustrate Huygens' principle. (Intro 1 figure) Point C touches the vacuum/material interface at time t=0 whereas point B is a distance d and point A is a distance 2d away from the interface.

Part B

What is the time t_B it will take for point B of the wavefront to encounter the vacuum/material interface?

Express your answer numerically to two decimal places in units of t₁ (the time it takes light to travel a distance d in a vacuum).

It should be noted that the accuracy of the method increases the smaller the distance is before making a new wavefront and redoing the wavelets. If you tried to just draw a large wavelet from point B, then it would hit the surface after only traveling a distance d. This large wavelet would make it difficult to visualize how to add up all of the other wavelets to make a coherent wavefront. As a result, one should just draw a line perpendicular to the wavefront at point B until it hits the surface, at which point the wavelets will change owing to the new index of refraction.

Part C

How far did point C go into the material interface in the time t=t_B that it took for point B to get to the interface? For this part we are looking for the distance traversed by the point C in the material (d_C).

Give your answer in terms of the time t_B, c, and n.

Part D

What is the new angle θ at which point C of the wavefront is propagating (relative to a line perpendicular to the vacuum/material interface)? Try to use the fact that you have a spherical wavefront propagating from t=0 at the point where C met the vacuum/material interface until time t_B when the wavefront at point B reached the interface.

Express your answer in terms of inverse trigonometric functions and n.

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Philosophy 2203E Chapter : Certain Truths.docx

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