MASTER MCAT PHYSICS

c = 3 × 10^8 m/s

speed of light in a vacuum (c) = ?

directly related

intensity (and energy) of light is _______________ (in/directly) related to the amplitude of light

radio wave < microwave < IR < visible light (ROYGBV) < UV < x-rays < gamma rays

rank from least to most energy (and frequency)

visible light (ROYGBV), x-rays, UV, gamma ray, IR, microwave, radio

gamma rays < x-ray < UV < ROYGBV < IR < microwave < radio wave

opposite of frequency and energy

rank from shortest to longest wavelength:

visible light (ROYGBV), x-rays, UV, gamma ray, IR, microwave, radio

1. reflection

2. refraction

3. absorption (don’t worry about it)

2 things that can happen when light encounters an interface between 2 media

reflection

the act of light bouncing off a given medium

angle of incidence EQUALS angle of reflection

refraction

wave bends when entering a new medium (its speed and angle refraction change, BUT frequency stays constant)

1. angle of refraction

2. speed

what 2 factors change when light is being refracted?

index of refraction

tells the ratio of the velocity in a vacuum (c) in relation to the velocity the medium (v)

n = c/Velocity_medium

index of refraction formula (n)

n = c/Velocity_medium

Snell’s law (calculate refraction) formula

n₁sinθ₁ = n₂sinθ₂

n is found from index of refraction formula: n = c/V_medium
θ is the angle of refraction

inversely

when n increase, angle refracted decrease, and vice versa

index of refraction (n) is ____________ (directly/inversely) related to angle refracted (θ₂)

toward

bc velocity would DECREASE, so light would fall closer to the 90 degree line perpendicular to medium

if n₂ > n₁, light bends ____________ (toward/away) from the normal

away

bc light travels faster with a smaller index of refraction, so it’d deviate from the normal

if n₂ < n₁, light bends ____________ (toward/away) from the normal

total internal reflection

light transmitting to a medium with a LOWER refractive index (does NOT refract → no bending light, 100% reflected, 0% refracted)

• 2 conditions must be met:

  • n₂ < n₁ so sinθ₂ > sinθ₁

  • increasing θ₁ leads to an even greater θ₂

1. n₂ < n₁ so sinθ₂ > sinθ₁

   1. ex: n₁ is water or glass, and n₂ is the air outside (n₂<n₁)

2. increasing θ₁ leads to an even greater θ₂

what are the two conditions of total internal reflection?

critical angle (θ_c)

the MINIMUM angle possible in order to maintain total internal reflection

in other words, it is θ₁ at which θ₂ = 90 degrees (max value bc that’s perpendicular to the NORMAL)… sinθ_c = n2/n1

90 degrees!

when θ_c is plugged into n₁sinθ_c, then θ₂ = ?

1. diffraction

2. dispersion

3. polarization

what are the 3 wave effects that light waves undergo?

diffraction

when waves encounter a small slit that’s same size as its length or smaller, the waves spread out. this is observable by light/dark pattern on a screen

dispersion

when wave spreads out all over bc its speed depends ONLY on the medium, not on frequency (which is not true for light)

different colors have different indexes of refraction → bends differently

faster, more

short wavelength = more energy/frequency, so waves travel faster, which leads to more bending

in terms of light dispersion, the shorter the wavelength, the ____________ (slower/faster) light travels in glass/water —> ___________ (more/less) light bending

polarization

wave effect that occurs when 1 direction of oscillation is PREFERRED over the other, either by reflection/transmission through medium (for transverse waves ONLY, not sound)

focal length (f)

the intrinsic property of lens/mirror that depends on index of refraction and curvature of the lens/mirror

convex/converging lens

type of lens that gives a positive focal length. lens that allow refracted light to meet → makes a real image (+i)

concave/diverging lens

type of lens that gives a negative focal length. lens that does not allow refracted light to meet → makes a virtual image (-i)

magnification (m)

the size of the image compared to the object that image came from

what does a positive magnification (+m) mean?

upright image

what does a negative magnification (-m) mean?

inverted image

focal length (f) formula

1/f = 1/o + 1/i

+f for convex/converging lens
-f for concave/diverging lens

inverted, -m

all real images (+i) are __________________ (inverted/upright) with a ___ (±) m

upright, +m

all virtual images (-i) are __________________ (inverted/upright) with a ___ (±) m

converge, positive f

concave mirrors _______________ (converge/diverge) light → f is __________ (positive/negative)

diverge, negative

convex mirrors _______________ (converge/diverge) light → f is __________ (positive/negative)

1/f = 1/i + 1/o m = -i/o

concave MIRROR → +f
1/6cm = 1/i + 1/15cm → i = 10cm
-10cm/15cm → m = -2/3.

image is inverted and 2/3 compared to size of object

object is placed 15 cm away from a concave mirror with focal length of 6cm. where is the image being formed? and how big is the image compared to the object?

magnification (m) formula

m = -i/o

myopia (near-sightedness)

condition where focal length of eye’s lens system is TOO SHORT. need glasses that’s a diverging lens to form image at retina.

diverging lens

people with nearsightedness (myopia) need __________ (converging/diverging) glasses lens

lens achieve clear vision by REFRACTION

squinting eyes achieve vision by DIFFRACTION

lens achieve clear vision by REFRACTION

squinting eyes achieve vision by DIFFRACTION

lens power

your glasses prescription (nearsighted = negative prescription… think about why. hint: what type of lens do nearsighted ppl use?)

P = 1/f

lens power formula

P = 1/f (in m^-1)

P = 1/f 1/f = 1/o + 1/i

-5 = 1/f → f = -1/5
-1/5 = 0 + 1/i (bc o was not given) → i = -1/5 = -0.2m

suppose your glasses have power of -5. where do your glasses form an image of a distant object?

hyperopia (far-sightedness)

condition where focal length of the lens’ system is TOO LONG. needs converging (convex) lens (positive prescription)

E = mc²

formula that relates mass to energy? (hint: albert einstein)

E = hf = hc/(lambda)

planck’s constant (h) = 6.62 × 10^-34

formula that relates nrg to frequency, plancks, and wavelength (2 formulas)

A.

convex lens produce real images bc the rays converge (meet), at which the image is inverted

what type of image is formed by a convex lens when the object is placed beyond the focal point?

A. real and inverted
B. real and upright
C. virtual and inverted
D. virtual and upright

A.

1/f = 1/i + 1/o m = -i/o

1/10 = 1/i + 1/15 → i = 30cm (pos bc concave mirror converge light)
m = -30/15 = -2. inverted and magnified

a concave mirror has a focal length of 10cm. an object is placed 15cm away from the mirror. what is the nature of the image formed?

A. real, inverted, and magnified
B. real, inverted, and reduced
C. virtual, upright, and magnified
D. virtual, upright, and reduced

B.

which of the following best describes the behavior of light rays when they pass through a converging lens?

A. light rays diverge after passing through the lens
B. light rays converge to a focal point after passing through the lens
C. light rays reflect off the lens in random directions
D. light rays continue in a straight line after passing through the lens

C.

they are asking to find lens power (P) = 1/f.
1/f = 1/o + 1/i
o = 1.0m, i = 0.02m

P = 1/f = 1/1 + 1/0.02
1/0.02 = 100/2 = 50 → 1 + 50 = 51 D

A person, whose eye has a lens-to-retina distance of 2.0 cm, can only clearly see objects that are closer than 1.0 m away. What is the strength S of the person’s eye lens? (Note: Use the thin lens formula ​​.)

A. –50 D

B. –10 D

C. 51 D

D. 55 D

B.

remember ohm’s law: V = CR (voltage = current * resistance)

When the current in a machine’s circuit increases and the resistance of the circuit remains constant, the voltage of the circuit:

A. decreases

B. increases

C. is constant

D. is zero

B.

n = c/v (c = speed of light)

n = 3E8 / 2.1E8 ~ 1.5

Knowing that the speed of light in the vitreous humor is 2.1 × 10⁸ m/s, what is the index of refraction of the vitreous humor? (Note: The speed of light in a vacuum is 3.0 × 10⁸ m/s.)

A. 0.7

B. 1.4

C. 2.1

D. 3

heat (Q)

transfer of non-mechanical energy b/w a system and its environment

related to the total thermal nrg of an object (measured in joules)

temperature (T)

macroscopic measure of the average internal (thermal) nrg of a system

energy (E) is the TOTAL energy, but the temp (T) measures the energy (E) of the INDIVIDUAL molecule

how are energy and temperature different?

intensive property

property that does NOT depend on the amount of material

extensive property

property that depends on the mass of material

closed system

system that allows NO exchange of matter

1. molecules cannot go in and out of the system

2. BUT still allows work to be done

Q = mCΔT

m = mass
C = specific heat of molecule
ΔT = temp change

formula for heat (Q)

phase change

process where system changes phase (gas, liquid, solid)

naur <3

its phase can change (solid, liquid, gas)

does adding heat to the system always change its temperature?

T increases and/or gas expands (or both)

If Q > 0 for an ideal gas:

1. what happens to T (increase/decrease)?

2. gas (expands/constricts)?

zeroth law of thermodynamics

law that states when 2 substances are in contact, heat transfers b/w them until they achieve the same temperature (thermal EQ)

1. conduction

2. convection

3. radiation

what are the 3 modes of heat transfer?

conduction

heat transfer through solids in contact

conduction

when you place a metal spoon in a hot cup of tea or coffee. The heat from the hot liquid is conducted through the metal spoon and into your hand as you hold it, warming your hand.

which heat transfer method is this an example of?

convection

heat transfer through fluids circulation

convection

when you boil water in a pot on a stovetop. As the water is heated, it becomes less dense and rises, carrying heat energy with it. Cooler water then moves in to take its place, and the process repeats, creating a continuous cycle of heat transfer through the movement of the water.

which heat transfer method is this an example of?

radiation

heat transfer by emission of electromagnetic energy (EM nrg)

radiation

the warmth you feel from the sun on a sunny day.

which heat transfer method is this an example of?

ΔE = Q - W

1. Q = heat added to the system

   1. Q > 0: heat ADDED to system

   2. Q < 0: heat LEAVES the system

2. W = work done BY the system

   1. W > 0: when system DOES work

   2. W < 0: when work done ON system

what is the internal energy of a closed system? (ΔE)

heat gets added to the system

what happens to the internal energy when Q > 0?

system does the work

what happens when W > 0?

work is done ON the system

what happens when W < 0?

system DOING work

W > 0

is expansion an example of work done ON the system or the system DOING the work?

also does that mean W __ 0? (<,>)?

work done ON the system

W < 0

is contraction an example of work done ON the system or the system DOING the work?

also does that mean W __ 0? (<,>)?

PV = nRT

ideal gas law formula

work (W)

gas expands → V increases → W > 0
gas contracts → V decreases → W < 0

for ideal gas, volume (V) is related to ___________

V increases, W > 0 (system does work)

when gas expands, what happens to volume (V) and work (W)?

V decreases, W < 0 (work done ON system)

when gas contracts, what happens to volume (V) and work (W)?

energy (E)

for ideal gas, temperature (T) is related to ___________

Q ≠ 0, W ≠ 0, or both

but E = Q - W still though

if an ideal gas transitions from 1 state to another (gas, solids, liquids). what happens to Q and W?

isobaric process

P = force / area

system has a constant pressure (ΔP = 0)

P = force / area

formula for isobaric processes to find pressure?

W = PΔV

SO… ΔE = Q - PΔV

formula to find work (W) and energy change (ΔE) in an isobaric system (ΔP constant)

isochoric process

system has a constant volume (ΔV = 0)

temperature rises… so pressure rises, and that’s it

for isochoric processes, what happens when heat is added? (Q > 0)

ΔE = Q (no W)

formula to find energy change (ΔE) in an isochoric process?

isothermal process

system in which temperature stays constant

volume increase… so pressure decreases

what happens to isothermal process when heat is added? (Q > 0)

Q = W

since temp change is 0, ΔE is 0 bestie

formula to find energy change (ΔE) in an isothermal process

adiabatic process

system in which there is no heat transfer (ΔQ = 0)

volume increases, pressure decreases, temperature decreases → nrg decreases

temp decrease bc gas molecules are doing work on the surroundings as they expand → reduction in kinetic energy

if volume increases in an adiabatic system, how does it affect V, P, T, and E?

temp decrease bc gas molecules are doing work on the surroundings as they expand → reduction in kinetic energy

why does temp decrease and energy decrease in an adiabatic process when volume increases?

ΔE = -W

formula to find ΔE energy change in an adiabatic system

entropy

measure of disorder of the system

isolated system

system in which neither energy nor matter is exchanged with the outside

(ΔE = Q - W cannot be applied)

closed system

system in which matter is NOT exchanged with outside environment, but energy can come in and out (ΔE = Q - W)

either stays the same or increases during any thermodynamic processes

how is entropy in an isolated system look?

can decrease, but only if the entropy of its surrounding environment increased by a greater amount

can entropy of a closed system decrease?

density = mass / volume

density formula