Pearls from MCAT practice exams

Question 1

Specific density refers to…

Answer 1

….how dense a substance is compared to water.

While technically, specific gravity can be defined relative to other reference fluids, on the MCAT you can assume that it refers to water unless the question or passage tells you otherwise. Specific gravity is a dimensionless constant, defined as ρ/ρwater. If a substance has a specific gravity greater than 1, it will sink in water.

Question 2

If a substance has a specific gravity less than or equal to 1, it will float, and the percentage of the object that will be submerged will equal its _______ _______ x ___.

Answer 2

specific gravity × 100

Question 3

Specific gravity is a _________ constant, defined as __/_____.

Answer 3

dimensionless

ρ_substance/ρ_water

Question 4

If you are comparing the wavelengths of two different lasers, and laser A has 10x longer wavelength than laser B, what other conclusions can you draw by knowing this?

Answer 4

Laser A will have a smaller energy difference between the normal state and the excited state.

Wavelength and energy are inversely related because of this equation: The energy E of a photon is equal to E = hv = hc/λ

Therefore, the higher the wavelength, the lower the energy.

(From Princeton Review, Practice Exam 1)

Question 5

Which has a shorter wavelength, blue or red light?

Answer 5

blue

Question 6

Diverging lenses cannot form ____ ______.

Answer 6

real images

(Princeton Review Practice Exam 1)

Question 7

The refractive index of a transparent medium ________ with increasing frequency of the transmitted light.

Trying rephrasing this in terms of wavelength.

Answer 7

increases

(The refractive index of a transparent medium increases with decreasing wavelength of the transmitted light.)