A laser beam of intensity I irradiates at normal incidence a face of area A of a cubical sample of intrinsic silicon of volume V. The photons from the laser beam are absorbed uniformly throughout the Si sample.

(i) If the quantum efficiency of intrinsic Si is ?, determine an expression for the electron-hole pair generation rate in the Si sample.   

(ii) Determine an expression for the excess carrier concentration, ??, under steady state conditions.

(iii) Calculate the ratio of the conductivity under illumination, ?light, to the conductivity without illumination, ?dark, for a Si sample of V =1 cm3,

A = 1 cm2, I = 1 mW cm-2, ? = 632.8 nm and ? = 0.3.

A physicist builds a parallel-plate capacitor with adjustable spacing between the plates. When the plates are at their initial separation, the capacitance is 7.00 µF.

(a) At this capacitance, the capacitor is connected to a 18.00 V battery. After fully charging, how much energy (in µJ) is stored in the capacitor?

(b) The battery is then disconnected. Without discharging the capacitor, the physicist then doubles the separation between the plates. At this point, how much energy (in µJ) is stored in the capacitor?

(c) Without changing this new separation between the plates, the capacitor is discharged, and then reconnected to the 18.00 V battery. Now, after fully charging, how much energy (in µJ) is stored in the capacitor?

A capacitor consists of two concentric spherical shells. The outer radius of the inner shell is a = 0.1 m and the inner radius of the outer shell is b = 0.2 m. a. What is the capacitance, C, of this capacitor? b. Suppose the maximum possible electric field at the outer surface of the inner shell before the air starts to ionize E max(r=a) = 3.0*10^6 V/m . What is the maximum possible charge on the inner capacitor? c. What is the maximum amount of energy stored in this capacitor? d. When E (r=a) = 3.0*10^6 V/m, what is the potential difference between the shells?

1. Find and read the following cases

• Jones v. Free Flight Sport Aviation , Inc. 623 P.370, Web 1981 Colo. Lexis 571, Supreme Court of Colorado.
• Flood v. Fidelity & Guaranty Life Insurance Co. 394 So 2d 1311; Web 1981 La App Lexis 3538 Court of Appeal of Louisiana.

2. Answer the following questions

• Should a person be allowed to disaffirm a contract he or she made as a minor after reaching the age of minority?
• What is a reasonable length of time after reaching the age of majority to permit disaffirmance?
• What ethical considerations are involved in these cases?

Question 10 (5 pts.):​ Why do you think cholera would choose to colonize the intestines of its host, as opposed to other parts of the body? (Try to think about what the bacteria might gain from living in the intestines.)

Question 11 (5 pts.):​ Why do you think it is important for ​V. cholerae​ to attach themselves firmly to the epithelial cells of the intestines, as shown in the picture above?

Question 12 (5 pts.):​ Suggest a reason why ​V. cholerae​ would benefit by causing their hosts to have excessive, watery diarrhea? How could this help the bacteria in their cycle of infection?

Consider the following special cases of collisions. In all cases, a cart of m1m1 comes in with a velocity vv and hits a cart m2m2coming in with velocity −v−v (same speed vv from the opposite direction). Most of these are answerable with either intuition or with mathematics. What are the final velocities of both carts if:

a. The collision is elastic, and both carts are the same mass? (Two swords collide in a swordfight)

b. The collision is inelastic, and both carts are the same mass? (Two identical twins charge-tackle each other)

c. The collision is elastic, and the mass of the first cart is much larger than the mass of the second cart? (Sword hits a dagger in a swordfight)

A professor tests whether the loudness of noise during an exam (low, medium, and high) is independent of exam grades (pass, fail). The following table shows the observed frequencies for this test.

Noise Level

Low Medium High

Exam Pass 20 18 8 46

Fail 8 6 10 24

28 24 18 N=70

(a) Conduct a chi-square test for independence at a 0.05 level of significance. (Round your answer to two decimal places.)

x^2{obt}=

(b) Compute effect size using Cramer's V. (Round your answer to two decimal places.)

V =

Ken has a coin that has probability 1/5 of landing Heads.

   Mary has a coin that has probability 1/3 of landing Heads.

   They toss their coins simultaneously, repeatedly.

Let X be the number of tosses until Ken gets his first Heads.

Let Y be the number of tosses until Mary gets her first Heads. Find:

Let U = min(X,Y) and V = max(X,Y)

(d) For k = 1, 2, 3,... , find a formula for P(U = k).

(e) For k = 1, 2, 3,... , find a formula for P(V > k). HINT: Inclusion-Exclusion.

The spin cycles of a washing machine have two angular speeds, 416 rev/min and 632 rev/min . The internal diameter of the drum is 0.560 m

Part A

What is the ratio of the maximum radial force on the laundry for the higher angular speed to that for the lower speed? (F higher/F lower)=?

Part B

What is the ratio of the maximum tangential speed of the laundry for the higher angular speed to that for the lower speed? (V higher/ V lower)=?

Part C

Find the laundry's maximum tangential speed . (m/s)

Part D

Find the laundry's maximum radial acceleration, in terms of g . (a rad=? g)