20. A photoelectric cell is made using emitting material with a work function of 2.00 eV. A constant voltage difference V is maintained between the emitting surface and the collecting surface in a direction to push electrons back towards the emitting surface. When the wavelength of the radiation is changed, the longest wavelength which produces a photocurrent is 350 nm. Calculate the voltage difference V. Answer in volts.
(A) 5.55
(B) 7.55
(C) 8.55
(D) 3.55
(E) 1.55

16. A charged capacitor is being discharged through a resistor. At the end of one time constant the charge has been reduced by (1 – 1/e) = 63% of its initial value. At the end of two-time constants the charge has been reduced by what percent of its initial value? (A) 82% (B) 100% (C) 86% (D) between 90% and 100% (E) 40%

17. A proton, traveling perpendicular to a magnetic field, follows a circular path with the same radius as an alpha particle which is also traveling perpendicular to the same field. The ratio of their speeds, v proton/v alpha is: (A) 0.5 (B) 4 (C) 1 (D) 2 (Ε) 8.

18. A square loop of wire moves with a constant speed v from a field – free region, through a region of uniform B field as shown. Which of the five graphs correctly shows the induced current I in the loop as a function of time t? (A)(B)(C)(D) g(E)

19. An unmagnetized steel bar is placed inside a solenoid. As the current in the solenoid is slowly increased from zero to some large value, the magnetization of the bar: (A) increases proportionally with the current (B) remains zero for a while and then increases linearly with any further increase in current (C) is unaffected by the current (D) increases with increasing current at first but later is much less affected by it (E) increases quadratically with the current.

1. A researcher hypothesizes that crocodile gender is determined by the incubation temperature of the egg. The researcher conducts experiments and determines that an average nest incubation temperature of 32 - 33°C results in the birth of male crocodiles, while higher and lower incubation temperatures result in female crocodiles. What is the most likely explanation for this phenomenon? (A) Since this phenomenon is influenced by an external stimuli (temperature), it cannot be attributed to changes in either the genome or the proteome. (B)Incubation temperature results in a change in the crocodilian proteome. (C) Incubation temperature results in a change in the crocodilian genome. (D) Incubation temperature changes both the crocodilian genome and proteome.

2. Which of the following is an example of horizontal gene transfer? (A) the transmission of an eye color gene from father to daughter (B)the transmission of a mutant gene causing cystic fibrosis from father to daughter (C) the transmission of a gene conferring pathogenicity (the ability to cause disease) from one bacterial species to another (D) the transmission of a gene conferring antibiotic resistance from a mother cell to its two daughter cells

3. Sickle cell anemia is a condition in which red blood cells exhibit a characteristic "sickle" shape. This arises from a mutation or change in one of the amino acids found in hemoglobin. A single amino acid mutation would directly affect a protein's _____ structure. (A) primary (B)secondary (C) tertiary (D) quaternary

4. If a specimen contains 30% adenine in its DNA, how much cytosine will it contain? (A) 40% (B)30% (C) 20% (D) 15% (E)10%

5. In order to visualize the fine structure of viruses and cytoskeletal filaments at 10-25 nanometers in diameter the type of microscopy that would be most effective is (A) standard light microscope (B)phase-contrast light microscope (C) transmission electron microscope (D) darkfield light microscope (E)confocal laser microscope

6. After drinking too much alcohol, a person will rely on which organelle to help detoxify and recover? (A) lysosome (B)smooth endoplasmic reticulum (C) mitochondrion (D) Golgi apparatus (E)peroxisome