AAMC CBT9 and 9R OFFICIAL Q&A

[Vihsadas]

This is the official Q&A thread for AAMC CBT9 and 9R.

Please post ONLY questions pertaining to AAMC CBT9 and 9R.
Out of respect for people who may not have completed the other exams, do not post questions or material from any other AAMC exam.

Please see this thread for the rules of order before you post.

Good luck on your MCAT!

---

Members don't see this ad.

 

[StarryNights]

Yea, I got confused with Kaplan's explanation for this too. I thought when light moves between two media that f stays the same, but since it's in a dense medium that the v = sqrt tension/linear density equation would make speed decrease so that wavelength decreases as well. I don't know why the wavelength increases according to kaplan explanation...

 

[Toolmatica]

Well, by convention if electrons absorb the light and emit it then the wavelength of the light must increase. Maybe a faulty problem? Maybe it's because it's the only answer choice that is physically possible. Not sure...

 

[RuSkaya]

Hey I'm confused about #7 on the PS section. I've read in previous exam explanations (other test companies) that ethers CAN hydrogen bond with water... they just cannot hydrogen bond with each other....

but in this explanation it says ethers cannot hydrogen bond with water (as opposed to ethanol, which can)

can somebody clear this up for me please?

 

[loveoforganic]

They can accept a hydrogen bond with a polarized hydrogen bond, they just have no polarized hydrogen bond themselves to donate.

 

[RuSkaya]

They can accept a hydrogen bond with a polarized hydrogen bond, they just have no polarized hydrogen bond themselves to donate.

Doesn't this mean that they can still hydrogen bond then? The question wasn't asking about who donates what just in general if the ether can hydrogen bond with water... I remembered the fact that ether has no hydrogen to donate but it didn't seem relevant.. Question was just asking what kind of interaction can alcohol have with water that ethers cannot? One of the options was H-bond and I immediately eliminated it... but it ended up being the right answer

 

[loveoforganic]

Could you post an image of the question? There might be subtle semantics at play. Or it might just be a crappy question.

 

[rls303]

Did anyone else get owned by the distylate passage with dialysis...to think I thought I did pretty well in Physio! Argh!

 

[zer0crew]

I've got some beef with question #30 of AAMC 9

The question asks:

What is the standard emf for the galvanic cell in which the following reaction occurs?

2 Na(s) + Cl2(g) ---> 2 Na+(aq) + 2 Cl-(aq)

Reduction Potentials (given)
Na+(aq) + e- ---> Na(s) -2.71v
Cl2(g) + 2e- ---> 2Cl-(aq) +1.36v

Correct Answer: +4.07v
My Answer: 6.78v

I understand that the Cl2 is being reduced. Ecell = Eright - Eleft
Ecell = E(reduction) - E(oxidationwrittenasareduction)
Gives us the equation;
Ecell = 1.36v - (-2.71v) = 4.07v

My problem with this set up is that it does NOT balance. To get the electrons to balance/cancel out, you need to multiply the Na equation by two.
Ecell = 1.36v - (2 x -2.71v) =6.78v

My question; Why does this equation not have to be balanced? Why does balancing this equation make it INCORRECT?

 

[wrigley09]

I've got some beef with question #30 of AAMC 9

The question asks:

What is the standard emf for the galvanic cell in which the following reaction occurs?

2 Na(s) + Cl2(g) ---> 2 Na+(aq) + 2 Cl-(aq)

Reduction Potentials (given)
Na+(aq) + e- ---> Na(s) -2.71v
Cl2(g) + 2e- ---> 2Cl-(aq) +1.36v

Correct Answer: +4.07v
My Answer: 6.78v

I understand that the Cl2 is being reduced. Ecell = Eright - Eleft
Ecell = E(reduction) - E(oxidationwrittenasareduction)
Gives us the equation;
Ecell = 1.36v - (-2.71v) = 4.07v

My problem with this set up is that it does NOT balance. To get the electrons to balance/cancel out, you need to multiply the Na equation by two.
Ecell = 1.36v - (2 x -2.71v) =6.78v

My question; Why does this equation not have to be balanced? Why does balancing this equation make it INCORRECT?

I'm not really sure why you don't balance when finding Ecell, but I know the rules. Only balance when you're finding the overall net equation. Don't balance for Ecell calculations. If I had to guess I'd say that it has something to do with flow of electrons...the whole point of these redox cells is to show us the flow of electrons, so it doesn't really make sense to balance the charge. Hopefully the mcat won't ask us for the theory behind it....luckily PS seems to be mostly calcs and not really much theory at all. But maybe someone else knows why you're not supposed to balance it.

 

[rls303]

I was wondering for the BS section for Item 22, is it not possible that you can undergo a methyl shift during a radical addition?

If it is, then wouldn't D be the best answer as it has the most methyl substituents.

 

[Ahhdumb]

My reasoning was that you don't want water to be lost from the blood. Hence the dialysate must be isotonic w.r.t the blood.

But kidneys function to get rid of excess water, the person has damaged kidneys and relies on dialysis to replace kidney function, wouldn't it make sense then that the high sodium in diasylate functions to draw water out of the blood? How else is this dude gonna pee? and the sodium conc in the diasylate is greater than the sick person so that was my reasoning behind picking A. Can anyone provide a good reason against this?

 

[Silverfalcon]

Doesn't this mean that they can still hydrogen bond then? The question wasn't asking about who donates what just in general if the ether can hydrogen bond with water... I remembered the fact that ether has no hydrogen to donate but it didn't seem relevant.. Question was just asking what kind of interaction can alcohol have with water that ethers cannot? One of the options was H-bond and I immediately eliminated it... but it ended up being the right answer

I agree with you. I know you took this exam several months ago so you probably won't see this, but for others, I think it's an incorrect question.

http://en.wikipedia.org/wiki/Ether#Physical_properties

Wikipedia may not be an elite source, but it does say that the presence of lone pairs of oxygen allows it to hydrogen bond with water. The question said "intermolecular" with "water," not "intramolecular" among themselves. Ugh.

 

[Handinhand]

Just took this test, and I didn't feel it was that bad at all, until I saw the curve at the end. 13,11,13. I got 49/52 on bio for a THIRTEEN? That's absurd! As well as a 48/52 on PS for a 13? Again, ludicrous.

 

[Silverfalcon]

Just took this test, and I didn't feel it was that bad at all, until I saw the curve at the end. 13,11,13. I got 49/52 on bio for a THIRTEEN? That's absurd! As well as a 48/52 on PS for a 13? Again, ludicrous.

The latter AAMCs have more steeper curve I believe. For instance, if you scored that in PS for Exam #10, it would be 12, not 13. Generally, real MCAT and practice MCAT are similar because real MCAT, while it's much harder, has more generous curve than practice MCAT.

 

[Merissa87]

Took this test today and it was so hard, my lowest score yet. I mad so many STUPID mistakes. Test is Tuesday 8/24 hopefully I can eliminate stupid errors by then!

 

[chemtopper]

From what I remember, anything with a NO3 will dissolve following the formula:

ANO3 --> A+(aq) + NO3-(aq)

NH4NO3 is an ionic compound and exists in completely dissociated form in water.So the key concept is ---you need to identify this compound as ionic or covalent .

 

[rls303]

Hi,
I don't see why the answer to this question is C.

In C4H9OCH3, you have an oxygen pair acceptor that can accept hydrogen bonds and in EtOH you can accept/donate hydrogen bonds. So then can't the C4H9OCH3 accept a hydrogen bond from water?

 

[donaldduck]

Hi,
I don't see why the answer to this question is C.

In C4H9OCH3, you have an oxygen pair acceptor that can accept hydrogen bonds and in EtOH you can accept/donate hydrogen bonds. So then can't the C4H9OCH3 accept a hydrogen bond from water?

C4H9OCH3 Is an ether and therefore doesnt have the charges sufficient to form hydrogen bonds. The hydrogens dont have a partial positive charge to form hydrogen bonds with the oxygen.

 

[Rabolisk]

C4H9OCH3 Is an ether and therefore doesnt have the charges sufficient to form hydrogen bonds. The hydrogens dont have a partial positive charge to form hydrogen bonds with the oxygen.

This question has been debated numerous times. Ethers can accept hydrogen bonds from water, but in this specific case, there may be steric hindrance. Regardless, clearly C is the best answer, even if the answer may or may not be true. But it is important, I think, to realize that ethers can hydrogen bond with water, just not amongst themselves.

 

[GodHelpMe85]

My reasoning as to question/item 16 is thinking about pressure and area. If you decrease the area of the vein, I would think that the pressure of the fluid would increase if of course the velocity is constant. If the pressure increases then the water is going to want to get out of the vein and push its way out into the interstitial space where the pressure is lower.... may make sense, may be totally wrong, but yet again my reasoning is quite different in all these questions.

And please people stop boasting about your scores... it doesn't freak people out, it just makes you sound annoying

 

[hiyaman]

I didn't see anyone ask this question but I was wondering why the lowest carbon to oxygen ratio would require the least to combust?

I looked up combustion, so is it because for each carbon you need more oxygen?

Also I thought the answer to this question was in the octane rating because the passage says that mixtures with higher octane rating burn slower, so i assumed it uses more oxygen as well.

 

[fizzgig]

the combustion question - yes.
the more carbons in the target, the more CO2 you need on the product side to balance. the more hydrogens in the target, the more waters you need on the product side to balance. the more water and CO2 on the product side you have, the more oxygen you need on the reactant side to balance.

 

[sekistudent]

Please help here.

I got stuck on this question because although the question stem states that the agnathan's were now classified with an earlier class of vertebrates that showed NO pituitary portal system, how can we definitively say with certainty that they represent an ancestral state? It is possible that this earlier group could have branched off (a long time ago) and degenerated from having a portal system. While rest of the vertebrates could have retained the portal system. The question stem is basically saying that the rest of the vertebrates must have followed the evolutionary line from this earlier group which agnathans belong to. But it doesnt allow for branching off??

thx

 

[WhiteWashed]

i hate that ether question. I still say MTBE can hydrogen bond with water via accepting the hydrogen from water.

 

[MilkIsGood]

nvm

 

[kycats]

PS #3:

Making which of the following changes to a circuit element will increase the capacitance of the capacitor described in the passage:

The answer is D, increasing the area of the capacitor plates. This makes sense, but I'm not sure why B, (replacing the 500 ohm resistor with a 250 ohm resistor) is incorrect--

Since C = Q/V and V = iR, it seems like lowering the resistance would decrease V, which would increase C.

Any thoughts?

 

[emericana]

How am I supposed to know that the volume is 22.4? I thought 22.4 was the volume for STP. STP is 25C not 0C? I would assume the volume would be different?

 

[Rabolisk]

STP is 0 degrees, not 25 degrees. Standard state refers to 25 degrees.

 

[emericana]

PS #3:

Making which of the following changes to a circuit element will increase the capacitance of the capacitor described in the passage:

The answer is D, increasing the area of the capacitor plates. This makes sense, but I'm not sure why B, (replacing the 500 ohm resistor with a 250 ohm resistor) is incorrect--

Since C = Q/V and V = iR, it seems like lowering the resistance would decrease V, which would increase C.

Any thoughts?

The formula you need to utilize is for the capacitance.

it states

C = k (e A)/d

really just focus on A and d

the capacitance is directly proportional to the area. so if you increase the area you increase C

if you were to increase d, the distance between the two plates, it would decrease the capacitance

 

[Rabolisk]

PS #3:

Making which of the following changes to a circuit element will increase the capacitance of the capacitor described in the passage:

The answer is D, increasing the area of the capacitor plates. This makes sense, but I'm not sure why B, (replacing the 500 ohm resistor with a 250 ohm resistor) is incorrect--

Since C = Q/V and V = iR, it seems like lowering the resistance would decrease V, which would increase C.

Any thoughts?

When you use this sort of mathematical reasoning, it's important that you not lose the meaning of the variables. V = iR is definitely correct, but what does it mean in this context? If you halve R, you would halve V, but only if i remained constant. In the context of the question, there is no current (a capacitor acts as an open circuit). In fact, there is no voltage drop across the resistor. However, for the sake of the discussion, let's say that V did halve. C = Q/V is correct, so halving V would double C, but only if Q was constant. But the V here refers to voltage across the capacitor which is not the same as that across the resistor (even if V across the resistor did halve, it is not the same as V across the capacitor). And then, even if V across capacitor did halve, you would have to make sure that Q was constant.

My point is that you don't want to rely on slippery math to get through physics. You should know that a capacitor's capacitance (and a resistor's resistance) is COMPLETELY INDEPENDENT of the circuit that it is in. It is only determined by its physical characteristics. A capacitor of 1 nanofarad capacitance has that same capacitance in any circuit. Only changing the capacitor itself can its capacitance change.

 

[golgiapparatus88]

I'm really happy with how I did on this test, 12,9,10 but question 47 on PS is confusing me

Visible light travels more slowly though an optically dense medium than through a vacuum. A possible explanation for this could be that the light:

The answer is A) is absorbed and re-emitted by the atomic structure of the optically dense medium.

I can see why that's right but my instinct was C) that it bounces around randomly inside the dense medium before emerging. The answer key says "Randomly bouncing around does not allow for the predictable nature of light to be upheld; therefore, we can eliminate choice." but I still feel like it's a good answer. Bouncing around wouldn't definitely slow it down. For example, the velocity of the speed of light in a medium is c/index of fraction so as the index of the medium increases, the speed decreases. Common sense would tell me the increased density would cause a large obstruction for the light wave to move.

Any help?

 

[JiniInBottle]

I had bought the exams long time ago, and printed the tests. But now I can't seem to find answers to Exam 9 questions from 136 through 141, for passage VII. I really appreciate it if someone can just post the answers for these few questions. Thank You!

 

[JiniInBottle]

Can someone please post the answers for questions 136-141?
I lost my answer sheet, my sister had bought it long time and printed the tests and answers so I don't have the answer for this passage, please.

Thanks!

 

[salim271]

This is only my second AAMC test but it seemed to go wayyyy better than AAMC 8... jumped from 28 to 35, and my lowest score was a 11 in verbal which is usually stronger for me. Verbal was the only place I literally had no time to go back. Hope my real test goes this well in a week and a half...

 

[mitchlucker]

Just took the test today...

12/8/15

Can someone please explain to me Passage 4 on verbal? I missed every question.

I seriously could not understand what it was trying to tell me...

Missed 1 question up until Passage 4 and it all went downhill from there...Wow...so disappointed.

Really mad that my EK verbal averages were about 10.5 and I take this and get an 8. It's the one section I really have to improve on this time around.

 

[mitchlucker]

I'm really happy with how I did on this test, 12,9,10 but question 47 on PS is confusing me

Visible light travels more slowly though an optically dense medium than through a vacuum. A possible explanation for this could be that the light:

The answer is A) is absorbed and re-emitted by the atomic structure of the optically dense medium.

I can see why that's right but my instinct was C) that it bounces around randomly inside the dense medium before emerging. The answer key says "Randomly bouncing around does not allow for the predictable nature of light to be upheld; therefore, we can eliminate choice." but I still feel like it's a good answer. Bouncing around wouldn't definitely slow it down. For example, the velocity of the speed of light in a medium is c/index of fraction so as the index of the medium increases, the speed decreases. Common sense would tell me the increased density would cause a large obstruction for the light wave to move.

Any help?

Yes, I put C as well and smacked myself for it when I saw the answer.

If it bounces around randomly inside, there's a chance that it will never leave!

 

[loreben]

Hi,
Can anyone please give a simplified indepth explanation to these questions. Thank you .

17) Which of the following mixtures, with each component present at a concentration of 0.1M has a pH closest to 7?
a)HClO(aq) and NaClO(aq)
b)HNO2(aq) and NaNO2(aq)
c)CH3COOH(aq) and NaCH3COOH(aq)
d)HNO3(aq) and NaNO3(aq)

19) When 2.0ml of 0.1M NaOH(aq) is added to 100mL of a solution containing 0.1M HClO(aq) and 0.1M NaClO(aq), what type of change in the pH of the solution takes place?
a)A slight (<0.1 pH unit) increase
b)A slight (<0.1pH unit) decrease
c)A significant (>0.1pH unit) increase
d)A significant (>0.1pH unit) decrease

 

[MT Headed]

Hi,
Can anyone please give a simplified indepth explanation to these questions. Thank you .

17) Which of the following mixtures, with each component present at a concentration of 0.1M has a pH closest to 7?
a)HClO(aq) and NaClO(aq)
b)HNO2(aq) and NaNO2(aq)
c)CH3COOH(aq) and NaCH3COOH(aq)
d)HNO3(aq) and NaNO3(aq)

19) When 2.0ml of 0.1M NaOH(aq) is added to 100mL of a solution containing 0.1M HClO(aq) and 0.1M NaClO(aq), what type of change in the pH of the solution takes place?
a)A slight (<0.1 pH unit) increase
b)A slight (<0.1pH unit) decrease
c)A significant (>0.1pH unit) increase
d)A significant (>0.1pH unit) decrease

It sounds like you need to review henderson/hasselbalch and buffer chemistry.

For question 17, we clearly have a case of buffers, meaning a solution that consists of the acid [HA] and its conjugate base [A-]. Remember, sodium is a spectator ion and not important to the discussion. What is the pH of a buffered solution? H-H tells us that pH = pKa + log([A-]/[HA]). Since the concentrations of acid and conj. base are equal, [A-]/[HA]=1 and log(1)=0. Therefore, pH = pKa. I'm assuming that they gave you a table of pKa values? Or if they gave you Ka values you would use pKa=-log(Ka) and the acid with a Ka nearest to 1x10^-7 would be the answer.

For question 19, again we have a buffer solution, a mix of a weak acid and its conj. base. A tiny amount of base is added to the buffer solution. What happens to the buffer? While you could do a lot of math to get the exact answer, this is just a conceptual question. Buffers resist changes to pH. Sure, you added a base, so the pH will go up a little. But it will go up only a tiny bit, because the concentrations of [A-] and [HA] will change a small amount.

Go look up "buffers" and "henderson hasselbalch" in whatever genchem resources you prefer to use.

 

[Joker88]

I think i may be over thinking this a little too much but on 41 but

PS Question 41

At which electrode is aluminum produced in a galvanic cell and in an electrolytic cell?

B. Cathode in both cells

I know that the cathode and anode swap places in a electrolytic cell in comparasion to a galvanic. Does the aluminum still get reduced in this case?

116. Which of these cycloalkanes will undergo free radical bromination most rapidly?

B. Cyclohexane w/ methyl off of carbon 2

I thought radicals are most readily formed when theyre most subsitituated. How come they picked the least substituated reactant?

131. When OB is incubated with a constant concentration of peptide A and increasing concentrations of B, osteoblatin concentration:

D. Decreases

I thought the concentration of the osteoblatin would stay the same. THe reason i had was that peptide A is being competed against by peptide B which would stop the creation of osteoblatin. So wouldnt the concentrate just stay the same as what it was before peptide A was competed against? Or is osteoblatin being used up consistently somehow?

 

[Joker88]

bump anyone??

 

[salim271]

I think i may be over thinking this a little too much but on 41 but

PS Question 41

At which electrode is aluminum produced in a galvanic cell and in an electrolytic cell?

B. Cathode in both cells

I know that the cathode and anode swap places in a electrolytic cell in comparasion to a galvanic. Does the aluminum still get reduced in this case?

116. Which of these cycloalkanes will undergo free radical bromination most rapidly?

B. Cyclohexane w/ methyl off of carbon 2

I thought radicals are most readily formed when theyre most subsitituated. How come they picked the least substituated reactant?

131. When OB is incubated with a constant concentration of peptide A and increasing concentrations of B, osteoblatin concentration:

D. Decreases

I thought the concentration of the osteoblatin would stay the same. THe reason i had was that peptide A is being competed against by peptide B which would stop the creation of osteoblatin. So wouldnt the concentrate just stay the same as what it was before peptide A was competed against? Or is osteoblatin being used up consistently somehow?

41. They dont swap, its just that in an electrolytic you're putting in energy to run the reaction instead of getting energy out of the reaction like you would in a galvanic.

116. In free radical bromination the hydrogen that is best removed is attached to a tertiary carbocation. Cyclohexane with a methyl at carbon 2 has a tertiary carbon, the hydrogen attached to said carbon is what is taken.

131. This one is weird, what's their explanation?

 

[MT Headed]

PS Question 41

At which electrode is aluminum produced in a galvanic cell and in an electrolytic cell?

Anode is oxidation.
Anode is oxidation.
Anode is oxidation.
(Anode and Oxidation are both vowels, Cathode and Reduction are consonants)
Or maybe you remember "Red Cat ("meow"); An Ox ("moo")".

In any event, when they start pulling the whole galvanic cell / electrolytic cell thing on you, just remember that anode is oxidation. Always. By definition. Everything follows from there.

If Aluminum (oxidation number 0) is being produced from Al3+ (oxidation number 3) then reduction is taking place, and it must be taking place at the cathode.

Always.

 

[Joker88]

For #131

The question asks the examinee to identify the relationship between the osteoblatin concentration and the increasing concentrations of peptide B when osteoblasting are incubated with a constant concentration of peptide A. Peptide A stimulates the production of the osteoblatin, but peptide B does not. Furthermore, Peptide B competitively inhibits Peptide A by binding to the same receptor sites on the cell membranes. As the concentration of the peptide B increases, more and more receptor sites are occupied by the peptide B rather than by Peptide A. This prevents peptide A from being able to activate expression of osteoblatin, therefore decreasing the osteoblatin concentration (D). A, B, C are incorrect becuase the osteoblatin concentration does not increase exponentially (A), increasing linearly (B), or remain constant (C). Thus, D is the best answer.

I can see why the answer is A if the osteoblatin is being used up but maybe i just over looked while answering the question.

also for the electrolytic cell...

I get that youre attempting to put energy into the system. Im just a little confused becuase I saw a picture in one of my books that had the cathode/anode switched in comparasion to a galvanic cell. The elements getting reduced and oxidized in the galvanic were Copper and zinc respectively. However, when they used the electrolyic cell the cathode and anode switched positions and they never switched the positions of the copper and zinc. So the Cu was getting oxidized and zinc was getting reduced...this was in BR chem btw

 

[muhali3]

I get that youre attempting to put energy into the system. Im just a little confused becuase I saw a picture in one of my books that had the cathode/anode switched in comparasion to a galvanic cell. The elements getting reduced and oxidized in the galvanic were Copper and zinc respectively. However, when they used the electrolyic cell the cathode and anode switched positions and they never switched the positions of the copper and zinc. So the Cu was getting oxidized and zinc was getting reduced...this was in BR chem btw

I got the question wrong too, but if you read it carefully, it says when aluminum is produced.

For aluminum to be produced, it has to be reduced from Al3+ to Al.

It's being reduced, so by definition it's at the cathode.

The BR example you gave above is correct. Anode just means where the electrons are coming from and cathode is just where the electrons are going. In galvanic cells, the electrons go where the naturally want to go. In an electrolytic cell, you force them to go the opposite way. So the anode and cathode switch.

 

[JiniInBottle]

I don't understand the question 137, nor the answer. can someone explain better? I think that the answer is a bit vague.

 

[MT Headed]

I don't understand the question 137, nor the answer. can someone explain better? I think that the answer is a bit vague.

So, normally the world goes DNA->mRNA->protein. However, if there was some complementary mRNA ("antisense mRNA") floating around too, it would naturally stick to the mRNA, and prevent it from being translated into a protein.

Question 137 suggests that instead of injecting or otherwise bathing the cytosol with antisense mRNA, why not just put the instructions for antisense mRNA into the genome? It's actually a cool idea.

mRNA (and antisense mRNA) are kind of unstable, so you would need to make both the mRNA and the antisense mRNA at the same time. It does no good to make a bunch of antisense mRNA an hour ahead of time, it would be long gone. So how can we guarantee that mRNA and antisense mRNA are made at the exact same time?

Answers A, B, and D suggest varying degrees of physical proximity between the mRNA and the antisense mRNA, which at first glance should maybe work. But the more you think about it, genes aren't transcribed at the same time because they are in close proximity. Genes have promoters and activators and all sorts of regulatory stuff that says when they should be transcribed. If two genes are regulated in similar manners (i.e. same promoters and activators and stuff) then (1) they will be transcribed at the same time, and (2) it doesn't matter if they are on adjacent DNA or on separate chromosomes.

That is what answer C says.

 

[JiniInBottle]

Thanks, that makes more sense.

 

[Sonyfan08]

Visible light travels mores slowly through an optically dense medium than through a vacuum. A possible explanation for this could be that the light:
A)is absorbed and re-emitted by the atomic structure of the optically dense medium
B) is absorbed and re-emitted by the nucleus of the material in the optically dense medium
c) bounces around randomly inside of the optically dense medium before emerging
d) loses amplitude as it passes through the optically dense medium

The answer is A. I chose D. Energy is proportional to amplitude. I thought that the reason why it traveled more slowly because it had lost energy along the way due to collision. And so because it lost energy = moves slower

 

[Sonyfan08]

item 96:

Why is answer A not the correct answer? I read the AAMC explanation, but I don't quite get it. If they found an agnathan skull with vascular connection, wouldn't that mean that the existing agnathan lost the connection. so, therefore present day agnathans are in degenerate state. How does this question differ from item 95?

 

[MT Headed]

I thought that the reason why it traveled more slowly because it had lost energy along the way due to collision. And so because it lost energy = moves slower

And to carry your thought experiment further, when the light leaves the dense medium and returns to air or a vacuum and speeds up, the light would somehow regain energy? from where?

No, this won't fly. Besides, the energy of a photon is related only to it's frequency (E=hf).