AST101H1 Study Guide - Midterm Guide: Electromagnetic Spectrum, Oort Cloud, Kuiper Belt

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emeraldgoldfish597

16 Oct 2011

School

UTSG

Department

Astronomy & Astrophysics

Course

AST101H1

Professor

Michael Reid

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AST101H1 Full Course Notes

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Document Summary

The material covered in term test 2 will include everything from the lecture on oct. 5 (tides) up to and including the lecture on nov. 4. Note that we are about 1 lecture behind, so that means that asteroids and. Comets in detail are not covered, though the general features of the entire. Solar system as discussed in earlier lectures are. Note that the overview of the solar system, as in the lecture of oct. 19th, is included (see ch. In the meantime, remember to focus your studying on the concepts covered in the lectures. Midterm 2 is cumulative, meaning that it may draw on concepts taught before midterm 1. However, the focus is definitely on material learned since the cut-off prior to the last midterm. Here are some of the key concepts we"ve covered since then: * the absorption of light by the atmosphere. * the three types of spectra: absorption, emission, and continuum.

Related Questions

t(s), d (cm), d (cm)
0, 12, 2
5, 15, 2
10, 20, 4
15, 25, 6
20, 29, 8

a) (10 points) One way to find the speed v from
the tabulated data is to calculate

v = ?d/?t

for each pair of successive times and then average
all ve values of v
(hint: the time intervals between successive points are all thesame). Show that this procedure gives

v = (d5 - d1)=(t5 - t1);

which means this method ignores the middle three measurements.Prove this without putting in numbers
(5 points); then nd a numerical answer (5 points). Make sure toshow all intermediate calculations.

b) (15 points) A better procedure is to make a least squares t tothe equation:

d = d0 + vt:

Using the formulas from the lectures notes, and working out thenumbers yourself,
make (by hand) an errorbar plot of d vs t, with t on the x-axis (3points)
calculate the slope (3 points) and its uncertainty (3 points)
calculate the intercept (3 points) and its uncertainty (3points)
You must do this by hand. Show all the required work. If you onlystate the results, you will receive
zero points even if they are correct. You can use MATLAB to checkyour calculations, but you do not
need to include it. However, remember to attach a print out of yourplot to your homework.

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Having so much trouble with this.. It seems simple.. but I amhaving a nightmare figuring where to start.

1a) Faraday discovered that a current is induced in a coil

A) only when the N pole of a magnet is inside the coil
B) only when the S pole of a magnet is inside the coil
C) only when there is a magnetic field inside the coil
D) only when the magnetic field inside the coil is changing

1b). A conductor moves through a uniform magnetic field at speed v and has a motional emf V created across it. If the conductor were to move twice as fast through the magnetic field, the motional emf would be:

A) V
B) 2V
C) 4V
D) V/2
E) V/4

1c) In the conducting rail discussed in section 25.2 (where the rail is moving at constant speed), what can you say about the power input due to the person pulling on the rail and the power dissipated in the resistance?

A) Power input from pull = power dissipated in R
B) Power input from pull > power dissipated in R
C) Power input from pull < power dissipated in R

1d) The electric generator as shown in the reading generates electricity by:

A) rotating a loop inside a magnetic field
B) moving a magnet in and out of a loop
C) sliding a loop over a magnet
D) running current through a loop in a magnetic field

1e) The magnetic flux through a loop:

A) is proportional to the number of magnetic field lines going through it
B) depends just on the B field going through the loop
C) is maximized when the B field lines in the plane of the loop
D) is zero when the B field is perpendicular to the plane of the loop
E) doesn't depend on the direction of the B field

1f) According to Lenz's Law, the induced B field (due to the induced current) will:

A) be in the opposite direction of the existing B field
B) be in the same direction as the existing B field
C) be in the same direction as the change in the existing B field
D) be in the opposite direction of the change in the existing B field

1g) A stationary coil experiences a doubling of its magnetic field (no change in direction of the field) in a time T and has a given induced EMF. If the same change were to have happened in half the time (T/2), the induced EMF would have been:

A) half as large
B) the same
C) twice as large
D) one-fourth as large
E) four times as large

1h) Eddy currents:

A) make it hard to pull a nonmagnetic material through a magnetic field
B) make it hard to pull a magnetic material through a magnetic field
C) speed up a magnetic material moving through a magnetic field
D) speed up a nonmagnetic material moving through a magnetic field

cerisejackal809

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.

greenduck607

AST101H1 Study Guide - Midterm Guide: Electromagnetic Spectrum, Oort Cloud, Kuiper Belt

AST101H1 Full Course Notes

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