GGRC44H3 Lecture 8: Lecture 8

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11 Dec 2011

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Corn lobby: corn growers, central part of usa, large scale corn farms, major investments to yield high production/efficiency. Intense impact in asia, lands being converted from forest to agrofuel production: especially palm oil, biodiversity loss, human displacement, strain on water and food supply. In brazil-sugarcane and soy for agrofuels: intensive energy required, agrochemicals. Do agrofuels reduce ghgs: ethanol reducing greenhouse gases, major studies: uminnesota, princetonu, skeptical of value, carbon debt-how long will it take to begin the benefits of agrofuel production. Extensive lands needed, land taken from food production, ecosystem restoration: moving towards efficiencies, need land for the fuel, land is taken out of food production and feedstock. Cellulosic myth: extraction costs, energy demands, wildlife, soil, water, biodiversity. Re-inflating the biofuel bubble": debate rages, subsidies and policies are supporting agrofuels. In 2000s: ethanol production tripled, biodiesel production increased nine-fold (uminneota study: most us $ (80%) towards agrofuelds, rather than solar/wind.

Related Questions

It is currently popular for automobiles to use 10% ethanol / 90%gasoline mixtures (âgasoholâ) as fuel. According to popularconsensus the main benefit of gasohol use is that it âreduces ourdependence upon foreign oil.â We test this assertion by making someelementary calculations. Our analysis will unrealistically ignoreengine maintenance issues associated with older automobiles (suchas gasket and seal hardening), added fuel consumption necessary toproduce grain used as a feedstock in ethanol production,incremental food price increases associated with a reduction ingrain stocks, and many other effects. Gasohol use typically reducesaverage fuel economy by approximately 15% and effectively leavesfuel prices unchanged. This article further debates the wisdom ofethanol use and may be of interest outside the problems:
http://harvardmagazine.com/2006/11/the-ethanol-illusion.html
These concerns and problems have been strongly influenced byconversations with Dr. H.J. Harmon, of the OSU physicsdepartment.

2. Consider a 14.2 mpg 1991 Ford F150 driven 761 miles. Calculatethe pure gasoline consumption of this truck when: a) usinggasoline, and b) when using gasohol (with its attendant economyreduction). Determine the total CO2 emissions for each fuelassuming all fuels produce 20 lbs of CO2 per gallon. Comment uponthe wisdom of using gasohol versus pure gasoline in this vehicle.

If a virtual image is formed 9.0 cm along the principal axis from aconvex mirror of focal length â15.0 cm, how far is the object fromthe mirror?

2. A woman looking in a makeup mirror sees her face at twice itsactual size and right-side up. If she is 26.0 cm from the mirror,what is its focal length?

3. Which of the following best describes the image of a concavemirror when the object is at a distance greater than twice thefocal point distance from the mirror?
a. virtual, upright and magnification greater than one
b. real, inverted and magnification less than one
c. virtual, upright and magnification less than one
d. real, inverted and magnification greater than one

4. A convex mirror with focal length of ?18 cm forms an image 12 cmbehind the surface. Where is the object located as measured fromthe surface?

5. A convex mirror with a focal length of ?18 cm forms an image 15cm behind the surface. If the object height is 1.2 cm what is theimage height?

6. An object placed 14 cm from a concave mirror produces a realimage 8.0 cm from the mirror. If the object is now moved to a newposition 18.0 cm from the mirror, where is the new image located asmeasured from the mirror?

7. When the reflection of an object is seen in a concave mirror theimage will:

8. A candle is 40.0 cm in front of a convex spherical mirror ofradius of curvature 70.0 cm. What are the image distance and themagnification, respectively?

9. An object is 16.0 cm from the surface of a spherical Christmastree ornament that is 8.00 cm in diameter. What is themagnification of the image?

10. A solid glass sphere with a radius of 6.00 cm and index ofrefraction of 1.50 has a small coin embedded 3.00 cm from the frontsurface of the sphere. For the viewer looking at the coin throughthe glass, at what distance from the front surface of the glassdoes the coinâs image appear to be located?

11. A glass block, for which n = 1.52, has a blemish located 4.5 cmfrom one surface. At what distance from that surface does the imageof the blemish appear to the outside observer?

12. An object of length 2.00 cm is inside a plastic block withindex of refraction 1.50. If the object is viewed from directlyabove, what is the length of its image?

13. An object is placed at a distance of 25 cm from a thin convexlens along its axis. The lens has a focal length of 10 cm. What arethe values, respectively, of the image distance andmagnification?
14. An object is placed at a distance of 50 cm from a thin lensalong the axis. If a real image forms at a distance of 35 cm fromthe lens, on the opposite side from the object, what is the focallength of the lens?

15. A contact lens is made of plastic with an index of refraction1.50. The lens has an outer radius of curvature of +2.0 cm and aninner radius of curvature of +2.5 cm. What is its focallength?

16. A Youngâs double slit has a slit separation of 2.50 ? 10?5 m onwhich a monochromatic light beam is directed. The resultant brightfringes on a screen 2.00 m from the double slit are separated by2.30 ? 10?2 m. What is the wavelength of this beam? (1 nm = 10?9m)

17. A Youngâs double-slit apparatus is set up so that a screen ispositioned 1.9 m from the double slits, and the spacing between thetwo slits is 0.040 mm. What is the distance between alternatingbright fringes on the screen if the light source has a wavelengthof 630 nm? (1 nm = 10?9 m)

18. The blue tint of a coated camera lens is largely caused by whateffects?

19. What is the minimum thickness of a glycerin film (n = 1.47) onwhich light of wavelength 650 nm shines that results inconstructive interference of the reflected light? Assume the filmis surrounded front and back by air.

20. Light of wavelength 560 nm is incident on a slit of width 0.150mm, and a diffraction pattern is produced on a screen that is 2.00m from the slit. What is the width of the central bright fringe? (1nm = 10?9 m)

21. Light of wavelength 610 nm is incident on a slit of width 0.25mm, and a diffraction pattern is produced on a screen that is 1.5 mfrom the slit. What is the distance of the second dark fringe fromthe center of the bright fringe? (1 nm = 10?9 m)

22. A multiple slit diffraction grating has a slit separation of2.50 ? 10?6 m. Find the wavelength of the monochromatic light thatwill have its second order bright fringe diffracted through anangle of 38.0Â°. (1 nm = 10?9 m)

23. A diffraction grating with 12 000 lines/cm will exhibit thefirst order maximum for light of wavelength 510 nm at what angle?(1 nm = 10?9 m)

24. A beam of unpolarized light in air strikes a flat piece ofglass at an angle of incidence of 58.0Â°. If the reflected beam iscompletely polarized, what is the index of refraction of theglass?

25. A beam of polarized light of intensity I0 passes through asheet of ideal polarizing material. The polarization axis of thebeam and the transmission axis of the sheet differ by 45Â°. What isthe intensity of the emerging light?

26. At what angle is the sun above the horizon if its light isfound to be completely polarized when it is reflected from the topsurface of a slab of glass (n = 1.65)?

GGRC44H3 Lecture 8: Lecture 8

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