intro
Question 1:
What is the formula for the Decay constant, denoted as "λ"?
Topic: Constants in Nuclear Physics
Correct Answer: A) -(ΔN/N)/Δt
- In the field of nuclear physics, the decay constant, represented as "λ," is a crucial concept that illustrates the rate of change in the number of atoms of a radioactive substance.
- It can be described mathematically as the negative of the ratio of the change in the number of atoms (ΔN) to the original number of atoms (N) per unit time (Δt).
- Therefore, the formula translates to "λ = -(ΔN/N)/Δt," which corresponds to option A. The negative sign indicates the reduction of the number of atoms due to decay over time.
Question 2:
In the context of radioactivity, how is the decay rate affected by electric and magnetic fields?
Topic: Radioactivity and Electromagnetic Fields
Correct Answer: D) It is not affected by electric and magnetic fields
- Radioactivity is a spontaneous, naturally occurring phenomenon that involves the decay of unstable atomic nuclei.
- This process happens at a specific rate known as the decay rate, which remains constant and is not influenced by external factors.
- Despite the seemingly pervasive effects of electric and magnetic fields on many physical phenomena, they do not have any impact on the rate of radioactive decay.
Question 3:
If radioactive Strontium-90 has a half-life of 30 years, what percentage of a Strontium-90 sample will remain undecayed after 60 years?
Topic: Half-life in Radioactive Decay
Correct Answer: C) 25%
- The half-life of a radioactive isotope is the time taken for half of its atoms to decay.
- After one half-life, 50% of the radioactive substance will have decayed.
- After two half-lives (60 years in this case), a further half of what remained after the first half-life will have decayed, leaving 25% of the original sample.
Question 4:
If the half-life of Iodine-131 is 8 days and the initial weight was 20mg, what will be the remaining undecayed weight after 4 half-lives?
Topic: Half-life Calculations in Radioactive Decay
Correct Answer: C) 1.25 mg
- Each half-life period reduces the undecayed amount of radioactive substance by half.
- After one half-life, the remaining amount is 10 mg (half of 20 mg). After two half-lives, it's 5 mg.
- After three half-lives, it's 2.5 mg. After four half-lives, it's 1.25 mg.
Question 5:
After four half-lives, what fraction of the original "N" radioactive nuclei in a sample will have decayed?
Topic: Decay of Radioactive Nuclei
Correct Answer: C) 15N/16
- A half-life is the interval in which half of the radioactive nuclei in a sample decay.
- With each passing half-life, the quantity of undecayed nuclei is halved. Hence, after one half-life, there are N/2 nuclei left, after two there are N/4, after three there are N/8, and after four there are N/16.
- The decayed nuclei are therefore N - N/16 = 15N/16.
Question 6:
In a Geiger counter, how are the metal tube and wire configured?
Topic: Geiger Counter Operation
Correct Answer: A) The metal tube acts as the cathode, and the wire acts as the anode
- A Geiger counter is a type of particle detector that measures ionizing radiation.
- Its operation includes a metal tube and a wire, which are configured with the metal tube acting as the cathode and the wire as the anode.
- This setup is fundamental to the operation of the Geiger counter, enabling the detection of ionizing particles.
Question 7:
Which radioactive isotope is the most useful as a tracer?
Topic: Radioactive Tracers
Correct Answer: D) Carbon-14
- Radioactive isotopes can be used as tracers in various scientific applications, including research in biology, chemistry, and geology.
- Among the options listed, Carbon-14 is the most useful tracer due to its ability to date organic material up to 60,000 years old.
- Its relatively long half-life and its interaction with living organisms make it ideal for this role.
MCQ 8:
Which of the following equations accurately depicts the nature of radioactive decay?
Topic: Radioactive Decay
Correct Answer: A) N = N0e-λt
- Radioactive decay follows a particular mathematical expression that characterizes the rate at which the decay occurs over time.
- The accurate equation for radioactive decay is N = N0e-λt, where 'N' is the number of atoms remaining, 'N0' is the initial number of atoms, 'λ' is the decay constant, and 't' is time.
- This equation is derived from the fact that the rate of decay is proportional to the number of radioactive atoms present.
- Therefore, the correct answer is A, "N = N0e-λt".
MCQ 9:
A radioactive isotope has a half-life of 6.5 hours. If the initial quantity of this isotope is 48×10³² atoms, how many atoms will remain undecayed after 26 hours?
Topic: Half-life in Radioactive Decay
Correct Answer: B) 3 × 10³²
- The half-life of a radioactive isotope indicates the time it takes for half of the isotope atoms to decay.
- In this problem, the half-life is 6.5 hours, so after four half-lives (26 hours), the remaining undecayed atoms will be (1/2)^4 of the original quantity, which is 3 × 10³² atoms.
- This is calculated by continuously halving the initial quantity for each half-life period.
- Therefore, the correct answer is B, "3 × 10³²".
MCQ 10:
What particle requires a minimum of three quarks to form?
Topic: Particle Physics
Correct Answer: C) Both proton and neutron
- In particle physics, quarks are fundamental constituents of matter.
- Protons and neutrons, which are hadrons, are made up of three quarks each.
- This means to form either a proton or a neutron, a minimum of three quarks is necessary.
- Therefore, the correct answer is C, "Both proton and neutron".
MCQ 11:
What is the common term used to refer to both protons and neutrons?
Topic: Nuclear Physics
Correct Answer: A) Nucleon
- Protons and neutrons are the main components of an atom's nucleus.
- The collective term used to describe both of these particles is 'nucleon'.
- They are distinct from mesons and bosons, which are different types of particles, and from quartz, which is a mineral.
- Therefore, the correct answer is A, "Nucleon".
MCQ 12:
If the half-life of a certain radioactive isotope is 140 days, after how many days will the isotope's decay rate reduce to one-fourth of its original decay rate?
Topic: Radioactive Decay
Correct Answer: B) 280
- The half-life of a radioactive isotope is the time required for half of its atoms to decay.
- After one half-life, the decay rate is halved, and after two half-lives, the decay rate becomes a quarter of the original rate.
- Therefore, after two half-lives, which equates to 2 * 140 = 280 days, the decay rate will be a quarter of its original value.
- Consequently, the correct answer is B, "280".
MCQ 13:
What are the possible units for the disintegration constant, also known as “λ”?
Topic: Radioactivity
Correct Answer: D) day⁻¹
- In the context of radioactivity, the disintegration constant, or decay constant, λ, represents the fraction of a number of atoms of a radioactive source that disintegrates in a unit time.
- As such, its unit is reciprocal of time (time⁻¹).
- In this case, given the options, the only unit that meets this criteria is 'day⁻¹'.
- Therefore, the correct answer is D, "day⁻¹".
MCQ 14:
On average, how many neutrons are released during the process of fission?
Topic: Nuclear Fission
Correct Answer: C) 2.5
- Nuclear fission is a reaction in which a nucleus splits, generally producing a significant release of energy.
- A characteristic feature of this process is the emission of a certain number of neutrons.
- On average, a typical fission reaction produces around 2.5 neutrons.
- Hence, the correct answer is C, "2.5".
MCQs 15:
Radium has a half-life of around 1600 years. If you start with 100g of radium, after how many years will only 25g of it remain without decaying?
Topic: Radioactive Decay
Correct Answer: D) None of these options
- The half-life of a radioactive element is the time it takes for half of the element to decay.
- With a half-life of 1600 years, 50g of the original 100g of radium would remain after 1600 years.
- After another half-life (another 1600 years), 25g would remain, totaling 3200 years.
- Thus, the correct answer is D, "None of these options".
MCQs 16:
Which of the following is considered the weakest of all known forces?
Topic: Fundamental Forces
Correct Answer: C) Gravitational force
- There are four fundamental forces known in physics: gravitational, electromagnetic, strong nuclear, and weak nuclear forces.
- Among these, the gravitational force is known to be the weakest.
- Despite its weakness on a subatomic level, its influence is universal and it governs the structure of the universe on a large scale.
- Therefore, the correct answer is C, "Gravitational force".
MCQs 17:
If radium has a half-life of approximately 1600 years, how much of a 1g radium sample will remain undecayed after a span of 6400 years?
Topic: Radioactive Decay
Correct Answer: C) 62 mg
- Radioactive decay is a natural process in which an unstable atomic nucleus loses energy by emitting radiation.
- A radioactive half-life refers to the amount of time it takes for half of a sample to decay.
- If radium's half-life is 1600 years, then after 4 half-lives (or 6400 years), the original 1g sample would have halved four times, leaving approximately 62.5 mg.
- Therefore, the correct answer is C, "62 mg".
MCQs 18:
Which type of nuclear decay is primarily associated with the weak nuclear force?
Topic: Nuclear Forces
Correct Answer: B) β decay
- The weak nuclear force is one of the four fundamental forces in nature and plays a key role in nuclear decay.
- Primarily, it is associated with beta decay, a process in which a neutron transforms into a proton while emitting an electron and an electron antineutrino.
- Therefore, the correct choice is B, "β decay".
MCQs 19:
What is the half-life of radium-226?
Topic: Radioactive Decay
Correct Answer: B) 1620 years
- The half-life of a radioactive isotope is the period of time it takes for a substance undergoing decay to decrease by half.
- Radium-226 is a radioactive isotope and its half-life is well established at approximately 1620 years.
- Therefore, the correct answer is B, "1620 years".
MCQs 20:
The activity (R) versus time (t) graph for three radioactive samples is provided. Arrange the samples in ascending order based on their half-lives.
Topic: Radioactive Decay
Correct Answer: B) 2, 1, 3
- Activity of a radioactive sample is directly related to the rate of decay, which is influenced by the half-life.
- A steeper curve on the graph indicates a faster rate of decay, hence a shorter half-life.
- Based on this, the order of half-lives, from shortest to longest, is sample 2, sample 1, and sample 3, respectively.
- Therefore, the correct answer is B, "2, 1, 3".
MCQs 21:
A 22Ne nucleus, after absorbing energy, decomposes into two α-particles and an unknown nucleus. Identify the unknown nucleus.
Topic: Nuclear Decay
Correct Answer: B) Carbon
- The α-particle, also known as a Helium nucleus, has a mass number of 4 and contains 2 protons and 2 neutrons.
- When 22Ne decays into two α-particles, the mass number decreases by 8 (4 for each α-particle) and the atomic number decreases by 4 (2 for each α-particle).
- The new mass number is 14 (22-8) and the atomic number is 6 (10-4), which corresponds to carbon.
- Therefore, the correct answer is B, "Carbon".
Question 22:
What is the process called when four hydrogen atoms merge to form a Helium atom?
Topic: Nuclear Reactions
Correct Answer: B) Fusion or thermo-nuclear reaction
- When lightweight nuclei combine to form a heavier nucleus, the process is called fusion.
- This reaction commonly occurs in stars, like our sun, where four hydrogen atoms fuse to form a helium atom.
- During this process, some of the mass is converted into energy, which is why it's also known as a thermo-nuclear reaction.
- Therefore, the correct answer is B, "Fusion or thermo-nuclear reaction".
Question 23:
Which of the following is a radioisotope?
Topic: Radioactive Isotopes
Correct Answer: A) Cobalt-60
- A radioisotope is an isotope that has an unstable nucleus and undergoes radioactive decay, releasing energy and particles until it reaches a stable state.
- Cobalt-60 is a commonly used radioisotope in medical applications, including cancer treatment, due to its radioactive properties.
- Therefore, the correct answer is A, "Cobalt-60".
Question 24:
In what circumstance do α, β, and γ-rays get emitted from a radioactive substance?
Topic: Radioactive Decay
Correct Answer: C) Spontaneously
- α, β, and γ-rays are types of ionizing radiation emitted by radioactive substances.
- These emissions occur spontaneously, as part of the radioisotope's transition to a more stable state.
- They do not require heating or interaction with other particles to be produced.
- Therefore, the correct answer is C, "Spontaneously".
Question 25:
If a pure 66Cu sample decays to Zn such that 7/8 of it decays in 15 minutes, what is the respective half-life?
Topic: Half-Lives
Correct Answer: C) 5 minutes
- The half-life of a radioisotope is the time taken for half the atoms in a radioactive sample to decay.
- In this case, 7/8 of the 66Cu sample has decayed in 15 minutes, which is equivalent to three half-lives.
- Therefore, dividing 15 minutes by 3 gives the half-life of 66Cu, which is 5 minutes.
- Hence, the correct answer is C, "5 minutes".
Question 26:
A radioactive isotope of silver bears a half-life period of roughly 7.5 days. What proportion of the original isotope remains after 15 days?
Topic: Half-Life
Correct Answer: A) 25%
- The half-life of a radioactive substance is the duration in which half of the initial quantity decays.
- In this scenario, the half-life is 7.5 days, and we are looking at a period of 15 days, which corresponds to two half-lives.
- After each half-life, the remaining isotope quantity is halved. Hence after 2 half-lives, the remaining quantity is (1/2)^2 = 0.25 or 25% of the original amount.
- Therefore, the correct answer is A, "25%".
Question 27:
How many fundamental forces exist in nature?
Topic: Fundamental Forces
Correct Answer: D) 4
- There are four fundamental forces that govern the interactions of particles in nature.
- These include the gravitational force, electromagnetic force, strong nuclear force, and weak nuclear force.
- Each force has its own unique properties and areas of influence.
- Hence, the correct answer is D, "4".
Question 28:
If a radioactive substance decays by 10% every 5 years, what will be the decayed percentage of the substance after 20 years?
Topic: Radioactive Decay
Correct Answer: A) 40%
- The question states that the radioactive substance decays at a rate of 10% every 5 years.
- To compute the decayed percentage in 20 years, we multiply the yearly decay rate by 4 (since 20/5 equals 4).
- Hence, the decayed percentage after 20 years is 10% * 4 = 40%.
- Thus, the correct answer is A, "40%".
MCQs 29:
What is the quantity of undecayed nuclei of a certain element after two of its half-lives have passed?
Topic: Half-Lives
Correct Answer: B) N/4
- A half-life is the period of time it takes for a substance undergoing decay to decrease by half.
- After one half-life, the quantity of undecayed nuclei would be N/2.
- After two half-lives, this quantity would halve again, resulting in N/4.
- Hence, the correct answer is B, "N/4".
MCQs 30:
Which of the following best describes the half-life of a radioactive element?
Topic: Radioactive Decay
Correct Answer: D) The period required for half of the substance to undergo decay.
- The half-life of a radioactive element is the time taken for half the atoms in a radioactive sample to decay.
- It is not associated with the total time it takes for the substance to decay, nor is it typically 50 years.
- The transformation from radium to lead is a specific example and not a general description of half-life.
- Therefore, the correct answer is D, "The period required for half of the substance to undergo decay".
MCQs 31:
Given two elements “A” and “B” with half-life times in the ratio of “TA/TB”, what is the ratio of their respective decay constants “λA/λB”?
Topic: Radioactive Decay Constants
Correct Answer: A) TB/TA
- The decay constant is a quantity that is inversely proportional to the half-life of a radioactive substance.
- Hence, if the half-lives of two elements are in the ratio TA/TB, their decay constants will be in the inverse ratio, i.e., TB/TA.
- The other options do not correctly represent this relationship.
- Therefore, the correct answer is A, "TB/TA".