MCAT physics chap 9 atomic and nuclear phenoms 16%
how wavelength is measures
" In nuclear physics, wavelength is commonly measured in nanometers (1 nm = 10−9 m) and ångströms (1 Å = 10−10 m)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
fusion
" occurs when small nuclei combine to form a larger nucleus. As an example, many stars (including the Sun) power themselves by fusing four hydrogen nuclei to make one helium nucleus " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Suppose a promethium-146 nucleus beta-decays as follows:" "What are the mass number and atomic number of the daughter isotope Y?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Again, balance the atomic numbers and mass numbers: Y must be samarium (Sm) because its atomic number is 62. Therefore, the daughter nucleus is " mass number stayds the same, atomic number changes
alpha dcay
"Alpha decay is the emission of an α-particle, which is a He 4/2 nucleus that consists of two protons, two neutrons, and zero electrons. The alpha particle is very massive compared to a beta particle and carries double the charge. Alpha particles interact with matter very easily; hence, they do not penetrate shielding (such as lead sheets) very extensively." "Alpha particles do not have any electrons, so they carry a charge of +2." "The emission of an α-particle means that the atomic number of the daughter nucleus will be two less than that of the parent nucleus, and the mass number will be four less. This can be expressed in the balanced equation:" azX->a-4z-2 Y + 42a
gamma radiation detection
"Because gamma radiation produces electromagnetic radiation (rather than nuclear fragments), it can be detected on an atomic absorption spectrum" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
half life stffs
"Because the amount remaining is cut in half after each half-life, the portion remaining will never quite reach zero. This is mostly a theoretical consideration; "all" of a sample is considered to have decayed after 7 to 8 half-lives." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Which of the following statements is inconsistent with the Bohr model of the atom? Energy levels of the electron are stable and discrete. An electron emits or absorbs radiation only when making a transition from one energy level to another. To jump from a lower energy to a higher energy orbit, an electron must absorb a photon of precisely the right frequency such that the photon's energy equals the energy difference between the two orbits. To jump from a higher energy to a lower energy orbit, an electron absorbs a photon of a frequency such that the photon's energy is exactly the energy difference between the two orbits." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
D "The Bohr model is based on a set of postulates originally put forward to discuss the behavior of electrons in hydrogen. In summary, these postulates state that the energy levels of the electron are stable and discrete, and they correspond to specific orbits, eliminating (A). They also state that an electron emits or absorbs radiation only when making a transition from one energy level to another, eliminating (B). Specifically, when an electron jumps from a lower-energy orbit to a higher-energy one, it must absorb a photon of light of precisely the right frequency such that the photon's energy equals the energy difference between the two orbits, eliminating (C). When falling from a higher-energy orbit to a lower-energy one, an electron emits a photon of light with a frequency that corresponds to the energy difference between the two orbits, This is the opposite of (D), which makes it the right answer." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Ultraviolet light is more likely to induce a current in a metal than visible light. This is because photons of ultraviolet light: have a longer wavelength. have a higher velocity. are not visible. have a higher energy." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
D "The photoelectric effect occurs when a photon of sufficiently high energy strikes an atom with a sufficiently low work function. This means that a photon with higher energy is more likely to produce the effect. Because ultraviolet light has a higher frequency and lower wavelength than visible light, it also carries more energy according to the equation E = hf. All light travels at the speed of light, eliminating (B). As mentioned earlier, ultraviolet light has a shorter wavelength than visible light, eliminating (A). The visibility of a wave plays no role in its ability to cause the photoelectric effect, eliminating (C)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Element X is radioactive and decays via α decay with a half-life of four days. If 12.5 percent of an original sample of element X remains after n days, what is the value of n? 4 8 12 16" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
D C "Because the half-life of element X is four days, 50 percent of an original sample remains after four days, 25% remains after eight days, and 12.5% remains after 12 days. Therefore, n = 12 days. Another approach is to set where x is the number of half-lives that have elapsed. Solving for x gives x = 3. Thus, 3 half-lives have elapsed, and because each half-life is four days, we know that n = 12 days." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"If the work function of a metal is 6.622 × 10-20 J and a ray of electromagnetic radiation with a frequency of 1.0 × 1014 Hz is incident on the metal, what will be the speed of the electrons ejected from the metal? (Note: h = 6.626 × 10−34 J·s and me− = 9.1 × 10−31 kg)" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
D C "To determine the speed of the electrons ejected, we must first calculate their kinetic energy: Now with a value for kinetic energy, we can calculate the speed of the ejected electrons: Notice the wide range in the exponents for the answer choices. While the math in this question may seem complex, this allows us to round significantly." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
threshold frequency
E= hf hey chem 1, H= 6.626 e-34, f= frequency energy of photon "Once we know the frequency, we can easily find the wavelength λ according to the equation c = fλ," "all-or-nothing" response: if the frequency of the incident photon is less than the threshold frequency (f < fT), then no electron will be ejected because the photons do not have sufficient energy to dislodge the electron from its atom. But if the frequency of the incident photon is greater than the threshold frequency (f > fT), then an electron will be ejected, and the maximum kinetic energy of the ejected electron will be equal to the difference between hf and hfT (also called the work function)" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
beta decay
"Beta decay is the emission of a β-particle, which is an electron and is given the symbol e− or β−. Electrons do not reside in the nucleus, but they are emitted by the nucleus when a neutron decays into a proton, a β-particle, and an antineutrino ( ). Because an electron is singly charged and 1836 times lighter than a proton, the beta radiation from radioactive decay is more penetrating than alpha radiation." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
electron capture
"Certain unstable radionuclides are capable of capturing an inner electron that combines with a proton to form a neutron, while releasing a neutrino. The atomic number is now one less than the original but the mass number remains the same. Electron capture is a rare process that is perhaps best thought of as the reverse of β− decay:" AZX + e-= AZ-1Y
"True or False: Small changes in chemical structure only minimally impact light absorption and emission patterns." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"False. Small changes, such as protonation and deprotonation, change in oxidation state or bond order, and others may cause dramatic changes in light absorption in a material." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Compare and contrast nuclear fission and nuclear fusion reactions:" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Fission Large (actinides, lanthanides) Decrease Fusion Small (hydrogen, helium) Increase" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
fission
"Fission is a process by which a large nucleus splits into smaller nuclei. Spontaneous fission rarely occurs. However, through the absorption of a low-energy neutron, fission can be induced in certain nuclei. Of special interest are those fission reactions that release more neutrons because these other neutrons will cause a chain reaction in which other nearby atoms can undergo fission. This in turn releases more neutrons, continuing the chain reaction. Such induced fission reactions power most commercial nuclear power plants." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
What causes fluorescence?
"Fluorescence is a special stepwise photon emission in which an excited electron returns to the ground state through one or more intermediate excited states. Each energy transition releases a photon of light. With smaller energy transitions than the initial energy absorbed, these materials can release photons of light in the visible range." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
gamma decay
"Gamma decay is the emission of γ-rays, which are high-energy (high-frequency) photons. They carry no charge and simply lower the energy of the parent nucleus without changing the mass number or the atomic number. The high-energy state of the parent nucleus may be represented by an asterisk." "Gamma decay questions are the easiest on the MCAT. No changes occur in the mass number or atomic number; only a γ-ray is emitted." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"If the half-life of a certain isotope is 4 years, what fraction of a sample of that isotope will remain after 12 years?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"If 4 years is one half-life, then 12 years is 3 half-lives. During the first half-life—the first 4 years—half of the sample will decay. During the second half-life (years 4 to 8), half of the remaining half will decay, leaving one-fourth of the original. During the third and final half-life (years 8 to 12), half of the remaining fourth will decay, leaving one-eighth of the original sample. Thus, the fraction remaining after 3 half-lives is ." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
flouresncens
"If one excites a fluorescent substance (such as a ruby, an emerald, or the phosphors found in fluorescent lights) with ultraviolet radiation, it will begin to glow with visible light. Photons of ultraviolet light have relatively high frequencies (short wavelengths). After being excited to a higher energy state by ultraviolet radiation, the electron in the fluorescent substance returns to its original state in two or more steps. By returning in two or more steps, each step involves less energy, so at each step, a photon is emitted with a lower frequency (longer wavelength) than the absorbed ultraviolet photon" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"If blue light of frequency 6.00 × 1014 Hz is incident on rubidium (W = 2.26 eV), will there be photoejection of electrons? If so, what is the maximum kinetic energy that an ejected electron will carry away? (Note: h = 6.626 × 10−34 J·s = 4.14 × 10−15 eV · s)" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"If the photons have a frequency of 6.00 × 1014 Hz, each photon has an energy of: E = hf = (4.14 × 10−15 eV · s)(6.00 × 1014 Hz) = 2.48 eV Clearly then, any given photon has more than enough energy to allow an electron in the metal to overcome the 2.26 eV barrier. In fact, the maximum excess kinetic energy carried away by the electron turns out to be: K = hf − W = 2.48 − 2.26 = 0.22 eV" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
half life
"In a sample of radioactive particles, the half-life of the sample is the time it takes for half of the sample to decay. In each subsequent half-life, one-half of the remaining sample decays so that the remaining amount asymptotically approaches zero." "Half-life problems are common on the MCAT. Make sure you write them out; it's easy to lose your place when doing them in your head." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
key concept beta decay
"In both types of beta decay, there needs to be conservation of charge. If a negative charge (β−) is produced, a neutron is converted into a proton to maintain charge. Conversely, if a positive charge (β+) is produced, a proton is converted into a neutron to maintain charge. Remember that negative beta decay produces a negative β-particle and positive beta decay produces a positive β-particle." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
positron emission
"In some cases of induced decay (positron emission), a positron is released, which has the mass of an electron but carries a positive charge. The positron is given the symbol e+ or β+. A neutrino (ν) is emitted in positron decay, as well." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
exponential decay
"Let n be the number of radioactive nuclei that have not yet decayed in a sample. It turns out that the rate at which the nuclei decay, N/T is proportional to the number that remain (n). This suggests the equation n/t= -λn Equation 9.11 where λ is known as the decay constant. The solution of this equation tells us how the number of radioactive nuclei changes with time. This is known as an exponential decay: n = n0e−λt " "where n0 is the number of undecayed nuclei at time t = 0. The decay constant is related to the half-life b" λ= ln2/.5t= .693/.5t
"How does the mass defect relate to the binding energy?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Mass defect is related to the binding energy such that there is a transformation of nuclear matter to energy with a resultant loss of matter. They are related by the equation E = mc2." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Complete the following chart:" " Emits... ΔZ ΔA Alpha decay Beta-negative decay Beta-positive decay Gamma decay Electron capture " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Nuclear Reaction Emits... ΔZ ΔA Alpha decay Alpha particle −2 −4 Beta-negative decay Electron (e−, β−) and antineutrino ( ) +1 0 Beta-positive decay Positron (e+, β+) and neutrino (ν). −1 0 Gamma decay Gamma ray (γ) 0 0 Electron capture Nothing (absorbs an electron from inner shell) −1 0" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
radioactive decay
"Radioactive decay is a naturally occurring spontaneous decay of certain nuclei accompanied by the emission of specific particles. On the MCAT, you should be prepared to answer three general types of radioactive decay problems: The integer arithmetic of particle and isotope species Radioactive half-life problems The use of exponential decay curves and decay constants" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"What electrical phenomenon results from the application of the photoelectric effect? " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The accumulation of moving electrons creates a current during the photoelectric effect." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
stability of nucleons
"The binding energy per nucleon peaks at the element iron, which implies that iron contains the most stable nucleus. In general, intermediate-sized nuclei are more stable than very large or small nuclei." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Measurements of the atomic mass of a neutron and a proton yield these results: p= 1.00728 n= 1.00867 He contains two protons and two neutrons, which should theoretically give a helium nucleus a mass of 2 × 1.00728 + 2 × 1.00867 = 4.03190 amu. However, the true mass of the helium nucleus is 4.00260 amu. What is the mass defect and binding energy of this nucleus? (Note: c^2= 932 )" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The difference 4.03190 − 4.00260 = 0.02930 amu is the mass defect for the helium nucleus. This is the mass that contributed to the binding energy of the nucleus: E= Mc^2= (.02930)(932)= .03x 900= 27 " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"What determines the absorption spectrum of a single atom?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The energy differences between ground-state electrons and higher-level electron orbits determine the frequencies of light a particular material absorbs (its absorption spectrum)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
key cocnept metals and electrons
"The energy of a photon increases with increasing frequency. The reason that we only discuss electrons being ejected from metals (and not protons or neutrons) is because of the weak hold that metals have on their valence electrons due to their low ionization energies." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"What are the four fundamental forces of nature?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The four fundamental forces of nature are the strong and weak nuclear forces, electrostatic forces, and gravitation" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Define the following terms: Strong nuclear force:" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The strong nuclear force is one of the four primary forces and provides the adhesive force between the nucleons (protons and neutrons) within the nucleus. Mass defect is the apparent loss of mass when nucleons come together, as some of the mass is converted into energy. That energy is called the binding energy." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"What does the threshold frequency depend upon?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The threshold frequency depends on the chemical composition of a material (that is, the identity of the metal)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"How does the work function relate to the energy necessary to emit an electron from a metal?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The work function describes the minimum amount of energy necessary to emit an electron. Any additional energy from a photon will be converted to excess kinetic energy during the photoelectric effect." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"If at time t = 0, there is a 2 mole sample of radioactive isotopes, how many nuclei remain after 45 minutes, assuming a decay constant of 2 hr−1? (Hint: = 0.22)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"This question is asking for an application of the exponential decay equation: n= noe^-yt= noe^(-2hr)(3/4)= noe^-3/2 Raising Euler's number (e) to an exponent—especially a fractional exponent—is beyond the scope of the math on the MCAT, but the value of is 0.22. Thus, 22% of the original 2 mole sample remains. This constitutes 0.44 mol, which, if multiplied by Avogadro's number, gives us the number of nuclei remaining:" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Suppose a parent nucleus X alpha decays as follows:" "What are the mass number and atomic number of the daughter isotope Y?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"To solve this question, we simply need to balance the atomic numbers and mass numbers: While it is not necessary to identify the elements to answer the question, answers on the MCAT are usually given with the element's symbol. Y must be thorium (Th) because its atomic number is 90. Therefore, the daughter nucleus is " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"True or False: Nuclear fission and nuclear fusion both release energy." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"True. While they may seem like inverses of each other, both nuclear fusion and nuclear fission reactions release energy." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"During which electronic transitions is photon emission most common?" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"When electrons transition from a higher-energy state to a lower-energy state, they will experience photon emission." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
MCAT expertise radioactive decay problems
"Whenever you approach radioactive decay problems on the MCAT, start by balancing the number of protons (the atomic numbers). Often, wrong answer choices will simply have an error in the number of protons and can be eliminated before even checking the mass numbers." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"A nuclide undergoes two alpha decays, two positron decays, and two gamma decays. What is the difference between the atomic number of the parent nuclide and the atomic number of the daughter nuclide? "
6 "In alpha decay, an element loses two protons. In positron decay, a proton is converted into a neutron. Gamma decay has no impact on the atomic number of the nuclide. Therefore, two alpha decays and two positron decays will yield a daughter nuclide with six fewer protons than the parent nuclide." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The figure below illustrates an electron with initial energy of -10 eV moving from point A to point B. What change accompanies the movement of the electron? Absorption of a photon Emission of a photon Decrease in the atom's work function Increase in the atom's total energy" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
B "The electron moves from a higher energy level to a lower energy level; this can only occur if the extra energy is dissipated through the emission of a photon. If the electron moved from B to A, it would absorb a photon and increase the atom's total energy; however, the opposite is occurring, so (A) and (D) can be eliminated. The work function is the amount of energy required to eject an electron from a material; when moving from A to B, the electrical potential energy of the atom decreases, meaning that more energy will be required to free the electron from the atom, eliminating (C)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"What is the wavelength of a photon that causes an electron to be emitted from a metal with a kinetic energy of 50 J? (Note: The work function of the metal is 16 J, and h = 6.626 × 10−34 J·s) 1.0 × 10−34 m 3.0 × 10−27 m 3.0 × 10−26 m 1.0 × 1035 m" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
B "To determine the wavelength of the light ray, first calculate its frequency from the photoelectric effect equation: In this case, estimation of Planck's constant makes our calculation much simpler without leading us to a nonviable answer. It is worth attempting an estimation first to avoid doing more work than necessary. Now we can determine the wavelength of the incident ray of light by relating the frequency to the speed of light: " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"When a hydrogen atom electron falls to the ground state from the n = 2 state, 10.2 eV of energy is emitted. What is the wavelength of this radiation? (Note: 1 eV = 1.60 × 10−19 J, and h = 6.626 × 10−34 J·s) 5.76 × 10−9 m 1.22 × 10−7 m 3.45 × 10−7 m 2.5 × 1015 m" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
B "To solve this question correctly, one must be careful with the units. First, convert 10.2 eV to joules: Next, to determine the wavelength of the radiation, we can combine the formulas E = hf and c = f λ: " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"What is the binding energy of the argon-40 isotope in MeV? (Note: mproton = 1.0073 amu, mneutron = 1.0087 amu, mAr-40 nucleus = 39.9132 amu, ) 0.4096 MeV 40.3228 MeV 381.7 MeV 643.8 MeV" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
B C "To determine the binding energy, we must first determine the mass defect. The mass defect is simply the masses of each of the protons and neutrons in the unbound state added together minus the mass of the formed argon-40 nucleus (which contains 18 protons and 40 − 18 = 22 neutrons): This math was difficult without a calculator, but by rounding one value down (proton) and one value up (neutron) by similar amounts we ended up very near the actual value. Calculating 18 x 7 = 126 and 22 x 9 = 198 for the decimal values is more manageable than the exact numbers and the spacing of the answer choices allows for our estimation. The binding energy can then be determined from this mass defect:" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"A certain carbon nucleus dissociates completely into α-particles. How many particles are formed? 1 2 3 4" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
C "A typical carbon nucleus contains 6 protons and 6 neutrons. An α-particle contains 2 protons and 2 neutrons. Therefore, one carbon nucleus can dissociate into particles." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Consider the following fission reaction. The masses of the species involved are given in atomic mass units below each species, and 1 amu can create 932 MeV of energy. What is the energy liberated due to transformation of mass into energy during this reaction? 0.003 MeV 1.4 MeV 2.8 MeV 5.6 MeV" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
C "This problem presents a reaction and asks for the energy liberated due to transformation of mass into energy. To convert mass into energy, we are told that 1 amu can be converted into 932 MeV of energy. All we need to do now is calculate how much mass, in amu, is converted in the reaction. Because we are given the atomic mass for each of the elements in the reaction, this is simply a matter of balancing the equation: Given both the small magnitude of this value and the small difference of the answer choices, it is best to not round at this point of the calculation. This is the amount of mass that has been converted into energy. To obtain energy from mass, we have to multiply by the conversion factor (1 amu = 932 MeV): " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"Which of the following correctly identifies the following process? β− decay β+ decay e− capture γ decay" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
C "This process can be described as electron capture. Certain unstable radionuclides are capable of capturing an inner electron that combines with a proton to form a neutron. The atomic number becomes one less than the original, but the mass number remains the same. Electron capture is a relatively rare process and can be thought of as the reverse of β− decay. Notice that the equation is similar to that of β+ decay but not identical because a particle is absorbed, not emitted." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"The half-life of carbon-14 is approximately 5,730 years, while the half-life of carbon-12 is essentially infinite. If the ratio of carbon-14 to carbon-12 in a certain sample is 25% less than the normal ratio in nature, how old is the sample? Less than 5,730 years Approximately 5,730 years Significantly greater than 5,730 years, but less than 11,460 years Approximately 11,460 years" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
C A "Because the half-life of carbon-12 is essentially infinite, a 25% decrease in the ratio of carbon-14 to carbon-12 means the same as a 25% decrease in the amount of carbon-14. If less than half of the carbon-14 has deteriorated, then less than one half-life has elapsed. Therefore, the sample is less than 5,730 years old. Be careful with the wording here—the question states that the ratio is 25% less than the ratio in nature, not 25% of the ratio in nature, which would correspond to (D)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"All of the following statements about the photoelectric effect are true EXCEPT: the intensity of the light beam does not affect the photocurrent. the kinetic energies of the emitted electrons do not depend on the light intensity. a weak beam of light of frequency greater than the threshold frequency yields more current than an intense beam of light of frequency lower than the threshold frequency. for light of a given frequency, the kinetic energy of emitted electrons increases as the value of the work function decreases." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
C A "The greater the intensity, the greater the number of incident photons and, therefore, the greater the number of electrons that will be ejected from the metal surface (provided that the frequency of the light remains above the threshold). This means a larger current. Remember that the frequency of the light (assuming it is above the threshold frequency) will determine the kinetic energy of the ejected electrons; the intensity of the light determines the number of electrons ejected per time (the current)." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
"A graph of an exponential decay process is created. The y-axis is the natural logarithm of the ratio of the number of intact nuclei at a given time to the number of intact nuclei at time t = 0. The x-axis is time. What does the slope of such a graph represent? λ − λ e−λt " Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
C. B "The expression n = n0e−λt is equivalent to Taking the natural logarithm of both sides, we get: From this expression, it is clear that plotting vs. t will give a straight line with a slope of −λ." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
kinetic energy of ejected e-
Kmax = hf − W "where W is the work function of the metal in question. The work function is the minimum energy required to eject an electron and is related to the threshold frequency of that metal by: W = hfT" Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
photoelectric effect
The emission of electrons from a metal when light shines on the metal eelctrons produce current provided frequency is above frequency threshold of metal " the greater the number of photons per unit time that fall on an electrode, producing a greater number of electrons per unit time liberated from the metal. When the light's frequency is above the threshold frequency, the magnitude of the resulting current is directly proportional to the intensity (and amplitude) of the light beam." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
atomic absorption spectrum
The unique spectrum of light absorbed when an atom's electrons are excited to higher energy levels. emissiion: photons given off as ligth when e- drops
isotope decay
parent nucleous X undergoes nuclear decay to form daughter nucleous Y azX-> a'z'Y + emitted decay particle "When balancing nuclear reactions, the sum of the atomic numbers must be the same on both sides of the equation, and the sum of the mass numbers must be the same on both sides as well." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
mass defect
the difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons later became E = mc2 "where E is energy, m is mass, and c is the speed of light. The mass defect is a result of matter that has been converted to energy." Excerpt From: Kaplan Test Prep. "MCAT Physics and Math Review 2021-2022." Apple Books.
