# OAT Test Prep: Physics Part 2

Article by Dale Paynter – Salus University 2014

Welcome to the second article for the Physics section of the OAT! In this article, I’ll be discussing the different study materials that helped me prepare for this section. As usual, there are free optometrystudents.com practice problems at the end, so enjoy!

Why is the Physics section generally regarded as one of the hardest sections to prepare for?

The main reason is that there just isn’t a whole lot of OAT-specific Physics material out there. This is largely due to the fact that the Physics section is the one section of the OAT that is not also found on the DAT (Dental Admission Test). And although there is plenty of MCAT material available for Physics, the MCAT has a somewhat different focus than the OAT; this limits the usefulness of MCAT material for pre-optometry students.

So what study material should you use? Kaplan does cover the Physics section in their OAT guides and classes, although I feel they should include more ‘concept’ questions (see my previous Physics article for an explanation of what these are) and they should have fewer problems requiring long calculations (most of the Physics problems are fairly straightforward). The closest thing I’ve found to the real test is, as usual, the ADA sample OAT test found here:

Under Step 4, just click on the link for the sample test! Note that there are a few errors in the answer key on this test, but overall this is an excellent, and free, study resource.

When I was studying for Physics, I made sure that I conceptually understood all of the formulas I was using. With this approach, I ensured that I wouldn’t accidentally apply the wrong formula to a problem, and this also made it much easier for me to answer the ‘concept’ questions. I do realize that this may take quite a bit of effort for some of you, but I do feel it is the best approach. If you must resort to simply memorizing equations, though (and I know many of you will) then make sure that you can apply the equations to problems asked in a variety of ways. You don’t want to miss a question that you know the equations for simply because you aren’t used to seeing the problem being asked in that way! Make sure you get plenty of practice, and you can start right now with these optometrystudents.com practice problems!

Problem 1:
Light of a certain wavelength traveling through air enters glass. Which of the following is NOT true?
A: The frequency of the light may change.
B: The direction the light is traveling may change.
C: The velocity of the light may change.
D: The wavelength of the light may change.

This is a good example of a ‘concept’ question, because no equations or numbers are given. To solve this problem, we can use two approaches. We can eliminate every answer that can be true, or we can directly identify the answer that cannot be true. The direction of the light may change according to Snell’s law, so we can eliminate choice B. The velocity of the light will certainly change (light travels faster in air than in glass), so we can eliminate choice C. And the wavelength is proportional to the velocity of the light, so if the velocity changes, the wavelength must change, so we can eliminate choice D. This leaves us with choice A as the only possible answer. Why is choice A correct? Well, the frequency of the light is directly related to the energy level of the photons, and the energy of the light certainly doesn’t change as light passes from one medium to the next (remember, energy cannot be created or destroyed, only converted) so we know that the frequency cannot change.

Problem 2:
A cannon fires a shell into the air at an angle of 60 degrees to the horizontal with a velocity of 100 m/s. As the shell reaches its maximum height, which of the following must be true? Ignore air resistance.
A: The horizontal component of velocity is decreasing.
B: The acceleration on the object becomes zero.
C: The vertical component of velocity reaches zero.
D: The shell has reached its maximum horizontal distance from the cannon.

This is a straightforward problem. We know that, ignoring air resistance, the horizontal component of velocity is constant, so we can eliminate choice A. We also know that the only acceleration on the object is due to gravity, and that this is constant, so choice B doesn’t make any sense. Choice C is correct, because at the maximum height for any projectile motion problem, the gravitational acceleration has exactly neutralized the object’s initial vertical velocity component. If it hadn’t (i.e. if the vertical component of velocity was still positive) then the object would go even higher, so it couldn’t have reached its maximum height yet! Choice D is clearly wrong, because it will reach its maximum horizontal distance from the cannon when the shell hits the ground.