Optional Assignment #3 Answers

1.
Is Point A in the figure below in a RIDGE or a TROUGH?  Would the winds at Point B blow toward the  NORTHEAST SOUTHEAST  SOUTHWEST  or  NORTHWEST?  Would you expect to find relatively  WARM  or  COLD  air below Point C?

The winds on upper level charts blow parallel to the contour lines from west toward east.


2.
Based on the directions and amounts of air movement at the surface and at upper levels, would you expect the surface pressure to  INCREASE,  remain the SAME,  or DECREASE?

There's a total of  25 + 25 = 50 units of air being added to the cylinder (all occurring at upper levels).  There are 25 units of air being removed at upper levels and 3 x 10 = 30 units being removed at the surface.  That is a grand total of 55 units.  There are 5 more units being removed than being added.  So the weight of the cylinder will decrease.  Since the surface pressure is determined by the weight of the air in the cylinder the surface pressure will also decrease.  Want some more practice?  Here is a link with more examples.

3.
The rate at which energy is transported through an object by conduction depends on the thermal conductivity of the material and on the temperature gradient.  Do you think energy would be transported more rapidly through   OBJECT A  or  OBJECT B  in the figure below?  (A has high thermal conductivity, B has low conductivity; the temperature gradients are the same)

Do you think energy would be transported more rapidly through  OBJECT C  or  OBJECT D  below. (Both materials have the same thermal conductivities, the temperature gradients are different)

What if there were no temperature difference or no temperature gradient.  In that case there wouldn't be any energy flow.

An analogous situation might be tripping and rolling down a slope.  You wouldn't roll very fast down a gradual slope.  You would roll much more quickly on a steep slope.

4.
A cold southward flowing ocean current (the California current) is found on the west coast of the United States, a warm northward current (the Gulf Stream) is found off the east coast.  Both currents transport energy from the tropics to the polar regions.  Oceans currents like these illustrate energy transport by
a. conduction              b. convection              c. electromagnetic radiation           d. latent heat

Many people would probably choose latent heat because water is involved.  But in order for latent heat energy transport to occur there must be changes in phase.  There is no mention of evaporating water or freezing water in this problem.

 Oceans currents are organized motions (of water molecules) however.  Organized motions of atoms or molecules in a gas or a liquid is convection.

Some people might worry about how a cold current transports energy.  When cold water moves leaves Location A and heads to  Location B it makes room for warm water (from somewhere else) to move into Location A.  That is how energy is being transported.

5.
Would a  positive charge placed at the x in the figure below, exactly half way between the + and - charges, move to the  RIGHT,  move to the   LEFT,  or  NOT MOVE  at all?

A positive charge placed at X would be repelled by the + charge at left and attracted to the - charge at right.

6.
Are Points A and B in the figure below exactly 1/4   1/2   3/4  or 1 wavelength apart?

You need to find identical points on the wavy pattern.   Points X and Y are also 1 wavelength apart, so are M and N.

7.
What was Isaac Newton able to demonstrate by shining white light through a glass prism?

Newton found that the white light was split into colors.  Newton demonstrated that what we perceive as white light is a mixture of colors.  You'll find a picture of this experiment in Fig.15.20 on p. 415 in the text.
8.
Is    UV-A     UV-B     or    UV-C    the most energetic form of electromagnetic radiation?  Does    VISIBLE light       MICROWAVE radiation       or       INFRARED light      have the shortest wavelength?

UV-C has wavelengths 0.2 to 0.29 micrometers, UV-B 0.29 to 0.32 micrometers, and UV-A 0.32 to 0.4 micrometers.  The shorter the wavelength, the more energetic the radiation.  Figure 2.6 on p. 32 gives typical wavelengths of visible (5 x 10-7 meters or 0.5 micrometers), IR light (10-6 meters or 1 micrometer) and microwave radiation (10-3 meters or 1000 micrometers)

9.
Which of the following is not a form of electromagnetic radiation?
a. gamma rays          b. radio waves          c. sound waves          d. x-rays

10.
Does filter absorption  CURVE A  or  CURVE B  correctly depict the behavior of the red filter shown below at left?
A red filter will absorb all colors except for red.  The filter transmits red light.  Curve A shows 0% absorption of 0.7 micrometer light (red light) and 100% absorption of all the other colors.

11.
The temperature of the tungsten filament in a bulb is about 3000 K.  What is the wavelength of peak emission?  What kind of light is that, can you see it?
We used Wien's Law to calculate lambda max.  This is near infrared radiation, it is invisible (at least for people, there may be some animals, or reptiles or insects that can see this kind of light).

12.
About half (49%) of the light emitted by the sun is    UV     VIS     IR     light.

44% of sunlight is visible light, the remaining 7% is ultraviolet light.

13.
How many total units of energy is being absorbed by the atmosphere?  The atmosphere is absorbing 3 units (1 unit of sunlight and 2 units of IR radiation emitted by the earth).
How many units of energy is being absorbed by the ground?  1 unit of sunlight makes it through the atmosphere and is absorbed by the ground.
How many units of energy must the atmosphere emit to be in radiative equilibrium?  Because it is absorbing 3 units, it must also emit three units.
How many units of energy must the ground receive from the atmosphere to be in radiative equilibrium?  The ground needs 2 more units of radiation to be in balance.
The 3 units of energy emitted by the atmosphere are shown in this figure.  2 units are sent downward to the ground to achieve energy balance there.  The third unit is sent up into space.


14.
There is an atmospheric greenhouse effect on the earth because
a. oxygen and ozone absorb UV light
b. condensation of water vapor releases energy into the air
c. carbon dioxide and water vapor (and all the other greenhouse gases) absorb IR light
d. water has a higher specific heat than soil
All of the statements are accurate.  However only c is part of the atmospheric greenhouse effect.

15.
Based on the information given (neither figure is in radiative equilibrium) would the temperature of the ground in Figure A below be  WARMER  COLDER  or the  SAME  as the ground in Figure B?

The important detail is that the ground is emitting the same amount of energy in both cases.  This is another of those Stefan-Boltzmann law ( "the rate at which an object emits energy depends on the object's temperature (to the 4th power)" ) questions.  The ground temperature must be the same in both figures for the ground to be emitting energy at the same rate.