Physics

Uranium has several isotopes with different numbers of neutrons. For example, Uranium-235 has 143 neutrons, while Uranium-238 has 146 neutrons, so the number of neutrons varies depending on the isotope.

Physical quantities are generally divided into two main categories: fundamental (or base) quantities and derived quantities. This classification helps in understanding and measuring physical phenomena.

Lead is a dense material with a high atomic number, making it very effective at absorbing and shielding against gamma rays compared to lighter materials like water or aluminum.

Radioactive decay follows an exponential decay law, expressed as N = N₀e^(-λt), where N is the quantity remaining, N₀ is the initial quantity, λ is the decay constant, and t is time. This formula correctly represents the decrease in quantity over time.

Pair production cannot occur in a vacuum because momentum cannot be conserved without a third body to take up recoil momentum. Energy, charge, and mass conservation are not violated, but momentum conservation requires interaction with a nucleus or another particle.

Gamma rays (γ-rays) have the greatest penetration power among the listed radiation types because they are high-energy electromagnetic waves that can penetrate most materials more deeply than alpha, beta, or neutron radiation under typical conditions.

Absolute uncertainty refers to the margin of error or the smallest unit that can be measured reliably by an instrument, which is typically related to the least count of the instrument. It does not depend on the magnitude of the measurement or the percentage error, which are related to relative uncertainty. Therefore, absolute uncertainty depends primarily on the least count of the instrument.

Beta particles are lighter and carry a single charge compared to alpha particles, which are heavier and doubly charged. Because beta particles have lower ionizing power, they lose less energy in collisions and thus have greater penetration power than alpha particles.

Alpha particles have much lower penetration power compared to beta particles because they are heavier and carry a double positive charge, causing them to lose energy quickly in matter. Typically, alpha particles penetrate only a few centimeters in air, whereas beta particles penetrate much further, making alpha particle penetration about 10 times less than beta particles.

The SI unit of torque is the newton-meter (N·m), which represents a force applied at a distance. Although joule (J) has the same units (N·m), it represents energy, not torque, so option A is correct.

Torque is the rotational equivalent of force and causes angular acceleration in a body. It does not directly cause linear acceleration or determine the direction of motion.

A beta particle is an electron emitted during beta decay, which carries a charge of -1 elementary charge.

When subtracting two measurements, the total uncertainty is the sum of their absolute uncertainties because uncertainties add regardless of whether quantities are added or subtracted.

Nuclei with the same mass number but different atomic numbers are called isobars. Isotopes have the same atomic number but different mass numbers, isotones have the same number of neutrons, and isomers are nuclei with the same atomic and mass numbers but different energy states.

Dimensional analysis is used to derive possible formulas by ensuring dimensional consistency and to check the homogeneity of physical equations, confirming that all terms have the same dimensions. It is not typically used for verification of laws, which requires experimental validation.

One atomic mass unit (AMU) is defined as exactly 1.66 x 10^-27 kilograms. The other options are incorrect or inconsistent with this standard value.

A smaller least count means the instrument can measure smaller increments, leading to more accurate measurements. Precision relates to the consistency of measurements, not directly to the least count.

In a single encounter, an alpha particle typically loses only a small fraction of its energy because it is a heavy, positively charged particle that interacts weakly with matter over short distances. It does not lose most or all of its energy in one collision.

The metric prefix 'deca' (also spelled 'deka') represents 10 raised to the power of 1, which means a factor of ten (10¹). This is confirmed by authoritative sources including the National Institute of Standards and Technology (NIST) and the International System of Units (SI) documentation. The symbol for deca is 'da'. Therefore, the correct answer is option A: '10 Raised to power 1'.

X-rays are commonly used in medical treatments, including skin treatments such as radiotherapy for skin cancers, due to their ability to penetrate tissues and target affected areas. Gamma rays are also used in radiotherapy but are less commonly used specifically for skin treatment compared to X-rays.

The average energy required to remove one nucleon from the nucleus is known as the binding energy per nucleon. This quantity indicates the stability of the nucleus and is a fundamental concept in nuclear physics.

Alpha particles can excite fluorescence in materials such as ZnS, barium platinocyanide, and calcium tungstate, so all of the listed substances can produce fluorescence when exposed to alpha particles.

The correct SI symbols for metric prefixes are case-sensitive and must be written directly attached to the unit symbol without spaces. 'mm' (millimeter) and 'km' (kilometer) are correct representations for one-thousandth and one-thousand meters respectively. However, 'um' is incorrect for micrometer; the correct symbol uses the Greek letter 'µ' (mu), so it should be written as 'µm'. Therefore, option C ('1000um') is not a correct representation, making C the correct answer to the question asking for the incorrect representation method.

Stokes' law applies to small spherical particles moving through a viscous fluid at low Reynolds numbers. The law specifically assumes the particle is spherical to calculate the drag force accurately.

Incompressible fluid means its density remains constant regardless of pressure changes. This is the defining characteristic of incompressible flow, making option C correct.