ISC Class 11 Physics Solutions

Explanation:
When the temperature of a pure semiconductor rises, its electrical resistance changes in response to the behavior of charge carriers within the material. Semiconductors have few free electrons at low temperatures, but as temperature increases, more electrons gain enough energy to jump from the valence band to the conduction band. This produces more charge carriers, affecting the resistance. The relationship is different from Metals, where resistance generally increases with temperature due to lattice vibrations. In semiconductors, initial heating may reduce resistance due to increased carrier generation, but further temperature rise can cause other effects like scattering. Conceptually, the resistance depends on both the number of free electrons and how easily they move. For example, in intrinsic silicon, the number of electrons in the conduction band grows exponentially with temperature, lowering resistance initially, while scattering mechanisms can eventually counteract this effect. In summary, a semiconductor’s resistance is highly sensitive to temperature because both carrier concentration and mobility change as thermal energy is supplied.

Explanation:
The energy from the sun travels through space to Earth via a process that does not require a material medium. Conduction and convection involve the transfer of Heat through direct contact or Fluid movement, which cannot occur in the vacuum of space. Instead, Solar energy propagates as electromagnetic waves, which can move through empty space without any particles. These waves carry energy in the form of photons, and when they reach Earth, they can be absorbed by surfaces, converted to Heat, or drive photosynthesis in plants. For instance, sunlight warming your skin occurs because photons strike and transfer energy to molecules in your skin. In summary, the sun’s Heat reaches Earth primarily through electromagnetic radiation, making this the only feasible method across the vacuum of space.

Explanation:
This question involves understanding the relationship between speed, distance, and time. Speed is defined as the distance traveled per unit time, and for a fixed distance, time is inversely proportional to speed. Therefore, if three cars travel the same distance but at different speeds, the time each takes can be calculated by taking the reciprocal of their speeds. For example, if one car moves slower, it takes more time, whereas the faster car takes less time. Here, the speeds are in the ratio 2:3:4, so the times will be in the reverse ratio to reflect the inverse relationship. Conceptually, this demonstrates the fundamental inverse relation between speed and travel time for a fixed distance. In summary, the ratio of times is the inverse of the speed ratio.

Explanation:
Conservative forces are those for which the work done on an object moving between two points is independent of the path taken and can be fully recovered as potential energy. Common examples include gravitational and electrostatic forces. Non-conservative forces, like friction, dissipate mechanical energy into other forms such as Heat and cannot be fully recovered. Identifying a non-conservative force requires understanding whether the work depends on the path. Friction opposes motion and converts energy into Heat, which is lost from the mechanical system, demonstrating that it does not conserve mechanical energy. For instance, sliding a block across a table involves work done by friction, which is not recoverable as potential energy. In summary, a non-conservative force dissipates energy and does path-dependent work.

Explanation:
Observation of objects is based on the behavior of Light. Light can reflect off surfaces, refract through media, or be absorbed by materials, allowing the human eye to detect objects. Reflection from surfaces is the primary mechanism for seeing most objects, while refraction allows the formation of images in lenses and optical instruments. Absorption determines the color and intensity perceived. For example, when sunlight hits a book, it reflects off the surface, enters our eyes, and forms an image on the retina, enabling vision. Thus, the combination of Light reflection, refraction, and absorption allows us to perceive our surroundings. In summary, the visibility of objects is primarily due to Light interacting with surfaces and reaching the observer’s eyes.

Explanation:
A dynamo is a machine that transforms one form of energy into another. Specifically, it converts mechanical energy, often from a rotating shaft, into electrical energy via electromagnetic induction. The basic principle relies on Faraday’s law, where a change in magnetic flux induces an electric current in a conductor. For example, turning the pedals of a bicycle connected to a small dynamo generates Electricity to power a headlight. This demonstrates the conversion of human mechanical effort into usable electrical energy. In summary, dynamos use motion and magnetic fields to produce electric currents for practical applications.

Explanation:
Nuclear reactors rely on controlled fission reactions, and moderators are materials that slow down fast neutrons, increasing the probability of further fission. Coolants remove Heat generated in the reactor core to prevent overheating. Certain substances, such as water or heavy water, are effective because they slow neutrons efficiently while simultaneously transferring Heat. Heavy water contains deuterium, which absorbs fewer neutrons than ordinary hydrogen, making it highly efficient as a moderator. For example, in CANDU reactors, heavy water serves both as a moderator and coolant. In summary, the choice of substance is crucial to sustain the fission chain reaction while safely managing thermal energy.

Explanation:
Photovoltaic cells, commonly called Solar cells, convert Light energy directly into electrical energy through the photovoltaic effect. When photons strike the cell, they excite electrons in a semiconductor, creating a flow of electric current. These cells typically use silicon, where the energy from sunlight generates electron-hole pairs that move under an internal Electric Field. For example, rooftop Solar panels use arrays of photovoltaic cells to supply Electricity to homes. This conversion does not involve mechanical motion or Heat engines, distinguishing it from other energy conversion devices. In summary, photovoltaic cells harness sunlight to produce Electricity directly.

Explanation:
A plane mirror reflects Light such that the angle of incidence equals the angle of reflection, producing an image behind the mirror at the same distance as the object in front. The image is upright, appears the same size as the object, and cannot be projected on a screen since it is virtual. For instance, when you look into a bathroom mirror, your reflection appears behind the glass but does not exist as a tangible projection. The light rays only appear to diverge from the point behind the mirror, which the brain interprets as an image. In summary, plane mirrors produce virtual, erect images at equal distances behind the mirror.

Explanation:
Capillary action is the phenomenon where liquids rise in narrow tubes due to the interplay of cohesive and adhesive forces. Adhesion between the liquid molecules and tube surface pulls the liquid upward, while cohesion between liquid molecules maintains the rise as a continuous column. Surface tension at the liquid-air interface also supports this effect. For example, water in a thin glass tube rises against gravity because of adhesion to the glass walls and cohesive interactions among water molecules. In plants, capillary action helps Transport water from roots to leaves. In summary, water climbs narrow tubes due to surface tension combined with Molecular adhesion and cohesion.

Explanation:
Terminal velocity occurs when the NET force on a falling object in a Fluid becomes zero, balancing gravitational force, buoyant force, and viscous drag. According to Stokes’ law, for a spherical object, terminal velocity depends on radius squared and density difference between the object and Fluid. If the Mass increases, assuming the same material, the volume and radius increase proportionally. Since terminal velocity is proportional to the square of the radius, a heavier sphere with eight times the Mass achieves a higher terminal velocity due to greater gravitational force overcoming viscous resistance. For example, larger raindrops fall faster than smaller ones due to this principle. In summary, the terminal speed increases with the size and Mass of the sphere in a viscous medium.

Explanation:
Viscous drag on a spherical object moving through a Fluid is described by Stokes’ law. The force opposing motion is proportional to the Fluid’s viscosity, the object’s radius, and its velocity. It is not inversely proportional; instead, the drag increases with size and speed. Mathematically, F = 6 π η R v, where η is the viscosity. For example, a small bead falling slowly in honey experiences less viscous resistance than a larger bead moving faster. This explains why drag scales directly with both radius and velocity. In summary, the resistive viscous force rises linearly with the sphere’s radius and speed in the Fluid.

Explanation:
The drag force on a sphere moving through a viscous Fluid is given by Stokes’ law: F = 6 π η R v, where R is the radius and v is the velocity. If both the radius and velocity are doubled, the force scales directly with both. Specifically, doubling R and v multiplies the force by 2 × 2 = 4. This means the new dragging force is four times the original. For example, a bead falling twice as fast and twice as large in honey experiences much greater resistance due to increased contact area and higher speed. In summary, drag increases proportionally with both the radius and velocity of the sphere.

Explanation:
Nuclear fusion involves the combination of light nuclei to form a heavier nucleus, releasing a tremendous amount of energy. This is the principle powering stars, including the Sun, where hydrogen nuclei fuse to form helium. Fusion requires extremely high temperatures and pressures to overcome the electrostatic repulsion between positively charged nuclei. Unlike fission, which splits heavy nuclei, fusion combines light nuclei to create energy and possibly other particles. For example, in the Sun, four hydrogen nuclei merge to produce one helium nucleus and energy. In summary, fusion releases energy by merging light atomic nuclei into heavier ones.

Explanation:
The Sun’s energy comes from nuclear reactions occurring in its core. Specifically, nuclear fusion converts hydrogen nuclei into helium, releasing energy in the form of light and Heat. These reactions require extremely high temperatures and pressures to overcome the Coulomb barrier between protons. Each fusion event releases energy according to Einstein’s relation, E = mc², where a small amount of Mass is converted to energy. For example, in the proton-proton chain reaction in stars, four hydrogen nuclei produce one helium nucleus and energy. In summary, the Sun’s energy originates from fusion of light nuclei under extreme conditions.

Explanation:
The hydrogen bomb, or thermonuclear weapon, was developed using nuclear fusion principles. It combines light nuclei like hydrogen isotopes to produce massive energy. Edward Teller is widely credited as the key scientist behind its design and development. Fusion-based bombs release energy far greater than fission-based bombs due to the higher energy per nucleon released when light nuclei combine. For example, the first successful hydrogen bomb tests involved fusion of deuterium and tritium to generate a massive explosion. In summary, the hydrogen bomb uses fusion reactions, and Edward Teller played a central role in its development.

Explanation:
Hydrogen bombs operate on the principle of nuclear fusion, where light nuclei combine to form heavier nuclei, releasing enormous energy. Unlike fission bombs, which split heavy atoms, fusion bombs require extreme temperatures to overcome the repulsion between nuclei. Fusion of isotopes like deuterium and tritium produces energy, neutrons, and helium nuclei. For instance, the detonation of a hydrogen bomb initiates a fission reaction that provides the heat necessary for fusion. In summary, the underlying principle of a hydrogen bomb is the fusion of light atomic nuclei under high-energy conditions.

Explanation:
The resistance of a wire depends on its resistivity, length, and cross-sectional area: R = ρ L / A. When the wire is stretched to double its length, the volume remains constant, so the area halves. Substituting L → 2L and A → A/2 into the formula gives R_new = ρ × 2L / (A/2) = 4R. This shows that stretching a wire increases its resistance significantly. For example, pulling a thin copper wire longer makes it thinner, which increases resistance. In summary, doubling the length of a uniform wire quadruples its resistance due to decreased cross-section.

Explanation:
For wires in series, total resistance is the sum of individual resistances: R_total = R₁ + R₂. Resistance is inversely proportional to cross-sectional area: R = ρ L / A. If the cross-section ratio is 3:1, the thinner wire’s resistance is three times that of the thicker wire. Given the thicker wire is 10 Ω, the thinner one is 30 Ω. Adding both gives 40 Ω as total resistance. For example, combining a thick copper wire with a thin one in series increases the total resistance as the thinner wire contributes more. In summary, series resistance sums the resistances, considering area differences.

Explanation:
Resistance depends on length and cross-sectional area: R = ρ L / A. Stretching the wire increases its length by 25%, but the volume remains constant, so the cross-section decreases proportionally. The new resistance is R_new = R × (L_new/L)² = 1 × (1.25)² = 1.5625 Ω. For instance, stretching a copper wire slightly makes it thinner, raising its resistance more than the length increase alone. In summary, a 25% increase in length causes a 56.25% increase in resistance due to the squared relationship with length.

Explanation:
Combining resistances can be done in series or parallel. For three equal resistors, combinations include: all in series, all in parallel, or one in series with two in parallel. Each arrangement yields a distinct effective resistance. For example, three 1 Ω resistors in series give 3 Ω, in parallel give 1/3 Ω, and one in series with two in parallel gives 1 + 1/2 = 1.5 Ω. This demonstrates the different possible combinations of the same resistors. In summary, three equal resistors can form three unique combinations with distinct resistances.

Explanation:
Specific resistance, or resistivity, is a material property independent of length and cross-section. Since both wires are made of copper, their resistivity is identical. Differences in length or diameter affect total resistance, not resistivity. For example, a long and short copper wire may have different resistances, but their specific resistance remains the same. In summary, wires of the same material always have the same specific resistance regardless of their dimensions.

Explanation:
Resistance is given by R = ρ L / A. Doubling the length (L → 2L) and doubling the cross-section (A → 2A) gives R_new = ρ (2L) / (2A) = ρ L / A = R. The changes cancel each other out. For example, a copper wire stretched to twice its length while also doubling its thickness keeps the resistance unchanged. In summary, doubling both length and cross-section leaves the resistance the same.

Explanation:
In a series connection, the NET electromotive force (emf) is the sum of the individual emfs, while current capacity remains determined by the cell with the smallest capacity. For instance, two 1.5 V cells in series produce 3 V across the terminals. Series arrangement adds voltages because the potential differences accumulate along the path. In summary, connecting cells in series increases NET emf, providing higher voltage to the circuit.

Explanation:
When a cell is not delivering current (open circuit), the potential difference across its terminals equals its electromotive force (emf). It represents the energy per unit charge provided by the cell. For example, a 1.5 V battery has 1.5 J of energy per coulomb available under no-load conditions. In summary, emf is the potential difference of a cell when no current flows.

Explanation:
A source providing a constant potential difference is called a source of emf. It maintains steady voltage regardless of current drawn (within limits) and drives current through a circuit. For example, a regulated battery or DC power supply supplies consistent voltage to electrical devices. In summary, a constant-potential source ensures continuous current flow by maintaining steady voltage.

Explanation:
The resistance within a cell due to its electrolytic solution is known as the internal resistance. It limits current flow and causes voltage drop when current passes. For example, a battery with high internal resistance delivers less current under load compared to one with low internal resistance. In summary, the electrolytic solution contributes to a cell’s internal resistance.

Explanation:
The capacity of a cell indicates how much electric energy it can supply before depletion. It depends on the quantity of reactive material in the electrodes and electrolyte. For example, a car battery with higher ampere-hour (Ah) rating lasts longer under the same load than a smaller battery. In summary, a cell’s capacity determines its total energy delivery potential.

Explanation:
In a parallel connection, the emf remains the same as a single cell, but the current capacity increases. This is because each cell contributes current to the total, reducing overall load on individual cells. For instance, two 1.5 V batteries in parallel supply the same 1.5 V but with greater total available current. In summary, parallel arrangement maintains voltage while increasing current supply.

Explanation:
Ohm’s law states that current through a conductor is directly proportional to voltage across it, provided temperature, dimensions, and material remain constant. Deviations occur if these factors change, as resistivity can vary with temperature. For example, metallic wires obey Ohm’s law under standard conditions but may deviate at high temperatures. In summary, Ohm’s law applies when material, temperature, and dimensions are constant.

Explanation:
Resistivity (ρ) is an intrinsic property of a material, independent of shape, length, or cross-section. It is influenced primarily by temperature and material type. For example, copper and aluminum have different resistivities, regardless of wire dimensions. In summary, resistivity depends on material and temperature, not geometry.

Explanation:
The unit of resistivity is ohm meter (Ω·m). Resistivity quantifies how strongly a material opposes current flow. For instance, copper has low resistivity (~1.68 × 10^-8 Ω·m), making it an excellent conductor, whereas rubber has very high resistivity. In summary, ohm meter is the standard unit to measure resistivity.

Explanation:
When an Electric Field is applied, free electrons in a conductor acquire a slow NET velocity called drift velocity. It is much smaller than their random thermal velocity but determines the current flow. For example, in a copper wire, electrons move randomly at ~10⁶ m/s but drift slowly at ~10^-4 m/s under applied voltage. In summary, drift velocity is the average velocity of electrons caused by an external Electric Field.

Explanation:
The work done per unit charge by a cell in moving a charge around a complete circuit defines its electromotive force (emf). It quantifies the energy converted from chemical to electrical form. For instance, a 1.5 V battery provides 1.5 J of energy per coulomb of charge circulated. In summary, emf represents the energy per unit charge delivered by the cell in a full circuit.

Explanation:
When identical resistors are connected in parallel, total resistance decreases. Cutting a wire into 4 pieces reduces the length of each segment, which decreases individual resistance, and placing them side by side forms a parallel combination. The effective resistance becomes R / 16. For example, four equal sections of wire in parallel conduct more easily than a single long wire. In summary, resistance reduces significantly in parallel arrangement.

Explanation:
Specific resistance (resistivity) is intrinsic to material and depends on temperature but not on geometric factors like length or cross-section. For example, doubling the length of a copper wire does not change its resistivity. In summary, resistivity is independent of wire dimensions but varies with material and temperature.

Explanation:
Resistance is proportional to length and inversely proportional to cross-sectional area. Stretching a wire doubles its length and halves its area (assuming volume is constant), giving R_new = 4 Ω × (2 / 0.5) = 16 Ω. For example, stretching a copper wire makes it thinner and longer, increasing resistance. In summary, stretching a wire increases resistance due to increased length and reduced area.

Explanation:
In Metals, electric current is carried by free electrons that drift under an applied Electric Field. Positive ions remain fixed in the lattice. For instance, in a copper wire, only electrons move to constitute current while the lattice ions are stationary. In summary, electric current in metallic conductors is caused by drifting free electrons.

Explanation:
Electric current is a scalar quantity representing the rate of charge flow through a conductor. Although charges move in a specific direction, current magnitude does not depend on direction like a Vector. For example, a 2 A current through a wire does not have Vector components; it is simply 2 A. In summary, current is considered a scalar quantity.

Explanation:
Electrons in a conductor move randomly due to thermal motion even without applied voltage, having different speeds and directions. The average drift velocity is zero. For instance, in a copper wire at room temperature, electrons move randomly at ~10⁶ m/s, but there is no NET current. In summary, electrons exhibit random motion before any potential difference is applied.

Explanation:
In parallel circuits, voltage across all resistances is the same. The current divides inversely with resistance; smaller resistance carries larger current. For example, a 2 Ω and 4 Ω resistor in parallel share the same voltage, but the 2 Ω resistor carries more current. In summary, parallel resistors have equal voltage but differing currents depending on resistance.

Explanation:
Ohm’s law holds when resistance remains constant, which requires temperature stability. Rising temperatures change resistivity in Metals, causing deviations. For example, a copper wire obeys Ohm’s law at room temperature but deviates if heated significantly. In summary, Ohm’s law is applicable only when conductor temperature is constant.

Explanation:
Bohr’s model describes electrons in fixed, quantized orbits around a massive nucleus that is considered stationary. Electrons do not radiate energy while in a stable orbit, and their Mass remains constant. For example, in the hydrogen Atom, electrons occupy discrete energy levels rather than spiraling into the nucleus. In summary, Bohr’s model assumes fixed electron orbits around a stationary nucleus with constant electron Mass.

Explanation:
Ionization energy is the energy required to remove an electron from the ground state of an Atom. For hydrogen, this energy corresponds to 13.6 eV per electron, representing the energy difference between the ground state and the point where the electron is free. For instance, photons with energy ≥13.6 eV can ionize hydrogen. In summary, hydrogen’s ground state ionization energy quantifies the energy needed to remove its electron.

Explanation:
The energy of an electron in hydrogen is negative relative to a free electron, indicating it is bound to the nucleus. The more tightly bound the electron, the more negative the energy. For example, the ground state has -13.6 eV. In summary, electron energy in bound orbits is negative, reflecting the stability of the Atom.

Explanation:
The Lyman series corresponds to electronic transitions where electrons fall to the n = 1 level. The emitted radiation has high energy, short wavelength, and lies in the ultraviolet region. For example, transitions from n ≥ 2 to n = 1 in hydrogen produce UV photons. In summary, the Lyman series is found in the ultraviolet portion of the Spectrum.

Explanation:
The electron-nucleus attraction is due to electrostatic (Coulomb) force between negatively charged electron and positively charged nucleus. For example, in a hydrogen Atom, this force keeps the electron in orbit. In summary, the central force binding electron to nucleus is electric in nature.

Explanation:
Nuclear radii are extremely small, typically 10^-15 m, so the fermi (1 fm = 10^-15 m) is most suitable. For example, a proton has radius ~0.84 fm. In summary, fermi is the standard unit for nuclear dimensions.

Explanation:
The atomic number (N) defines the number of protons in an element, which determines its chemical properties. Atomic weight (W) is total mass of protons and neutrons. For example, carbon has N = 6, so 6 protons are present. In summary, the proton count in a nucleus equals the atomic number.

Explanation:
The nucleus contains protons and neutrons, which account for nearly all atomic mass. Electrons orbit outside the nucleus. For instance, hydrogen-1 has 1 proton, 0 neutron in the nucleus. In summary, protons and neutrons are the nuclear constituents.

Explanation:
Boiling occurs when vapor pressure equals atmospheric pressure. At high altitudes, air pressure is lower, so water reaches boiling point at a lower temperature. For example, on Mount Everest, water boils near 70°C instead of 100°C. In summary, reduced air pressure at high elevations lowers the boiling temperature.

Explanation:
Energy per photon is proportional to frequency (E = hν). X-rays have higher frequency than visible, microwave, or radio waves, hence higher photon energy. For example, X-ray photons can ionize atoms, whereas radio waves cannot. In summary, higher frequency waves like X-rays carry maximum energy per photon.

Explanation:
Bats use echolocation, emitting ultrasonic waves and detecting reflections to navigate and locate prey. Ultrasonic waves have frequencies above human hearing, allowing precise obstacle detection. For example, a bat’s 50 kHz calls reflect off insects, providing spatial information. In summary, bats rely on reflected ultrasonic waves for orientation and hunting.

Explanation:
X-rays, microwaves, and radio waves are electromagnetic waves, while sound waves are mechanical and require a medium. For instance, radio waves can travel in vacuum, whereas sound cannot. In summary, sound waves differ fundamentally from the electromagnetic waves listed.

Explanation:
Barometers measure atmospheric pressure using liquids like mercury, water, or Alcohol. The liquid column height balances atmospheric pressure. For example, mercury barometers are standard due to high density and low vapor pressure. In summary, barometers use liquids to reflect changes in atmospheric pressure.

Explanation:
X-rays are high-energy electromagnetic radiation with very short wavelengths capable of penetrating materials. They are not visible to the naked eye. For instance, X-rays are used in medical imaging to see internal structures. In summary, X-rays are short-wavelength electromagnetic radiations.

Explanation:
Radioactivity is quantified using detectors like the Geiger-Müller counter, which registers ionizing radiation events. For example, a GM counter clicks for each radioactive decay detected. In summary, the GM counter measures the intensity of radioactive emissions.

Explanation:
Convex mirrors provide a wider field of view and diminished image size, making them suitable for rear-view applications. For example, a convex mirror allows a driver to see multiple lanes of traffic simultaneously. In summary, convex mirrors are ideal for rear-view mirrors due to wide-angle coverage.

Explanation:
A biprism splits light into two coherent sources with fixed phase relationships, enabling interference patterns. For example, Young’s double-slit experiment uses biprism to generate coherent waves. In summary, a biprism is used to produce coherent light sources for interference studies.

Explanation:
White light contains multiple wavelengths; each produces different fringe spacing. This leads to colored fringes near slits, merging to uniform illumination further away. For instance, thin film interference shows rainbow colors. In summary, white light produces few colored fringes and then uniform illumination.

Explanation:
Unequal amplitudes reduce contrast in interference. Destructive interference does not fully cancel light; intensity in dark regions is nonzero. For example, in overlapping laser beams with different intensities, dark fringes appear dim rather than fully dark. In summary, unequal amplitudes lead to partial interference with some intensity in destructive regions.

Explanation:
Steady interference requires coherent sources: same frequency, constant phase difference, and ideally equal brightness. For instance, two lasers of the same wavelength produce stable fringes. In summary, coherence ensures fixed phase relationships and steady interference patterns.

Explanation:
Equal brightness means the two sources emit waves of the same amplitude. Amplitude determines light intensity, so identical amplitude ensures uniform fringe visibility in interference experiments. For example, two identical lasers produce fringes with consistent brightness. In summary, equal amplitude makes light sources equally bright.

Explanation:
Fringe overlap occurs if slit width is too large. To resolve distinct fringes, slit width should be slightly less than fringe width. For instance, narrow slits in Young’s experiment produce clear, separated interference fringes. In summary, slit width must be just smaller than fringe width for non-overlapping fringes.

Explanation:
When two waves are 180° out of phase, destructive interference occurs. Their amplitudes cancel completely, producing zero NET amplitude. For example, two sound waves of equal amplitude but opposite phase produce silence at overlap. In summary, perfectly opposite waves result in zero resultant amplitude.

Explanation:
High contrast occurs when the intensities of the two waves are equal. Maximum constructive and destructive interference is achieved, giving clear bright and dark fringes. For instance, equal-intensity lasers produce sharp interference patterns. In summary, equal wave intensities maximize fringe contrast.

Explanation:
Interference requires a constant phase difference. Identical wavelength alone is not enough; coherence ensures phase difference remains fixed over time. For example, two laser beams with stable phase relationships produce visible fringes. In summary, constant phase difference allows steady interference.

Explanation:
Fringe contrast depends on the intensity ratio of the two sources. Greater disparity reduces visibility; equal intensities produce bright, distinct fringes. For instance, mismatched lasers result in faint fringes. In summary, fringe contrast is determined by source intensity ratio.