Physics: Practice Questions with Answers
Motion, energy, light, electricity, and everyday physics. Try each question first: tap an option to check it, and the explanation appears below.
Question 1Easy
What type of radioactive decay involves the emission of a helium nucleus consisting of two protons and two neutrons?
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✅ C. Alpha decay
Alpha decay is a radioactive transformation wherein an unstable atomic nucleus ejects an alpha particle comprising two protons and two neutrons, identical to a helium nucleus. This emission reduces the parent nucleus mass number by four and atomic number by two, resulting in a different daughter element. Such natural transmutation processes are fundamental concepts in nuclear physics and radioactivity.
Question page →Question 2Medium
What happens to the resonant frequency of an LCR series circuit if the value of the capacitance is increased?
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✅ B. It decreases
The resonant frequency of a series LCR circuit is expressed mathematically as f equals one divided by the product of two pi and the square root of inductance and capacitance. Since capacitance is located in the denominator under the square root, an increase in capacitance causes a corresponding decrease in the resonant frequency. Inductance and capacitance determine the rate of energy oscillation between the magnetic and electric fields in the circuit. Tuning circuits in radio receivers rely directly on varying capacitance to select specific frequencies.
Question page →Question 3Medium
When a ray of light enters a denser medium from a rarer medium, which of the following characteristics of light changes due to the change in wave velocity?
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✅ B. Wavelength and velocity only
When light travels from one optical medium to another, its speed and wavelength change in proportion to the refractive index of the media, whereas its frequency remains strictly constant because frequency is determined solely by the source of light. The refractive index is defined as the ratio of the speed of light in vacuum to the speed of light in the medium.
Question page →Question 4Medium
What is the primary reason why incandescent light bulbs are filled with an inactive gas like argon or nitrogen instead of being left under vacuum?
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✅ B. To prevent the rapid evaporation and oxidation of the tungsten filament
Incandescent bulbs are filled with inert gases such as argon or nitrogen to suppress the vaporization of the hot tungsten filament at high operating temperatures, thereby extending bulb lifespan. A vacuum would cause the tungsten atoms to sublimate rapidly and deposit on the inner glass surface. Nitrogen and argon molecules collide with evaporating tungsten atoms and knock them back onto the filament.
Question page →Question 5Hard
A double convex thin glass lens having a refractive index of 1.5 is placed in a transparent liquid medium whose absolute refractive index is precisely 1.6. How does the optical behavior of this lens change upon immersion?
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✅ A. The lens behaves as a diverging lens because the surrounding medium is optically denser than the lens material
According to the lens maker formula, when a lens is immersed in a medium whose refractive index exceeds that of the lens material, the sign of the focal length term reverses, transforming a converging convex lens into a diverging concave lens. Retaining convergence requires the lens refractive index to exceed the surrounding medium value. Refraction does not cease unless refractive indices match identically. Total internal reflection occurs only past critical incidence angles rather than normal lens immersion. The focal length magnitude also scales inversely with the relative refractive index difference.
Question page →Question 6Hard
Which physical law states that the magnitude of the induced electromotive force in a closed circuit is directly proportional to the time rate of change of magnetic flux linked with the circuit?
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✅ B. Faraday law of electromagnetic induction
Faraday law of electromagnetic induction quantifies how changing magnetic fields generate electrical voltage in conducting loops. Lenz law provides the negative sign indicating the direction of the induced current to oppose the flux change. Ampere law relates magnetic fields to electric current enclosing them.
Question page →Question 7Hard
What is the name of the phenomenon in which a superconductor completely expels all magnetic fields from its interior when it is cooled below its critical temperature?
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✅ B. Meissner Effect
The Meissner effect describes the complete expulsion of magnetic field lines from the interior of a superconductor when it is cooled below its critical transition temperature. The Zeeman effect involves the splitting of spectral lines in the presence of an external magnetic field. This property confirms that a true superconductor acts as a perfect diamagnet.
Question page →Question 8Hard
A particle executes simple harmonic motion along a straight line with an amplitude of 0.05 meters and a frequency of 10 hertz. What is the maximum acceleration experienced by the particle during its motion?
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✅ B. 20 pi squared meters per second squared
The maximum acceleration in simple harmonic motion is given by the product of the square of the angular frequency and the amplitude, where angular frequency equals two pi times frequency. Substituting the given values yields an angular frequency of twenty pi radians per second, and squaring this gives four hundred pi squared, which when multiplied by zero point zero five gives twenty pi squared meters per second squared. Simple harmonic motion represents the periodic oscillation of a body about a stable equilibrium point.
Question page →Question 9Hard
A particle performs simple harmonic motion along a straight line with an amplitude of ten centimeters and a time period of four seconds. What is the magnitude of its acceleration at the instant when its displacement from the mean position is equal to five centimeters?
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✅ A. Five point zero multiplied by pi squared centimeters per second squared
The magnitude of acceleration in simple harmonic motion is given by the product of the square of angular frequency and the displacement from the mean position. Angular frequency equals two pi divided by the time period of four seconds, yielding half pi radians per second. Squaring this angular frequency and multiplying by the five centimeter displacement yields five point zero times pi squared centimeters per second squared. Incorrect options arise from miscalculating the angular frequency or substituting the full amplitude instead of the instantaneous displacement. The restoring force in simple harmonic motion is always directed towards the equilibrium position.
Question page →Question 10Medium
Which of the following physical laws states that the line joining a planet and the Sun sweeps out equal areas in equal intervals of time?
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✅ B. Kepler's Second Law
Kepler's Second Law describes how planets move faster when closer to the Sun and slower when farther away, sweeping out equal areas in equal times, driven by conservation of angular momentum. The first law deals with elliptical orbits, and the third relates orbital period to semi-major axis distance. These laws apply universally to orbiting bodies in astrophysics.
Question page →Question 11Easy
Which of the following optical phenomena explains why a swimming pool appears shallower than its actual measured depth?
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✅ B. Refraction of light
The refraction of light causes a swimming pool to appear shallower than its actual depth because light rays bend as they travel from the denser water medium into the rarer air medium. When these refracted rays reach the human eye, they appear to originate from a higher virtual position due to optical bending. Refraction is also responsible for phenomena such as the twinkling of stars and the apparent bending of a stick immersed in water.
Question page →Question 12Easy
Which instrument is used to measure the high temperatures of distant stars and radiant bodies?
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✅ A. Pyrometer
A pyrometer measures high temperatures remotely by detecting thermal radiation, making it ideal for furnaces and stellar bodies where direct contact is impossible. Hydrometers measure liquid density instead of temperature. Pyrometry relies on Stefan-Boltzmann law principles to calculate radiant energy.
Question page →Question 13Easy
Which type of magnetic material is strongly attracted by a magnet and can be permanently magnetized?
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✅ C. Ferromagnetic
Ferromagnetic materials like iron, cobalt, and nickel exhibit strong positive magnetic susceptibility and can retain permanent magnetization even after the external magnetic field is removed. In contrast, diamagnetic materials are weakly repelled by magnetic fields, whereas paramagnetic substances show weak attraction.
Question page →Question 14Easy
Which law or principle establishes that the magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux?
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✅ B. Faraday's law of induction
Faraday's law of electromagnetic induction states that the magnitude of the electromotive force induced in a closed circuit is directly proportional to the time rate of change of magnetic flux linking the circuit. Lenz's law complements this by determining the directional polarity of the induced current to oppose the flux change. This principle forms the foundational operating mechanism for electrical generators and transformers.
Question page →Question 15Hard
A Carnot engine operates between a source at five hundred kelvin and a sink at three hundred kelvin. If the engine absorbs twelve hundred joules of heat from the source in each cycle, what is the work done by the engine per cycle?
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✅ A. Four hundred and eighty joules
The efficiency of a Carnot engine is calculated as one minus the ratio of the sink temperature to the source temperature, which gives forty percent for the given temperatures. The work done per cycle is equal to the product of the thermal efficiency and the heat absorbed from the source, yielding four hundred and eighty joules. The second law of thermodynamics establishes that no heat engine operating between two temperatures can be more efficient than a reversible Carnot engine.
Question page →Question 16Medium
Which type of material exhibits negative magnetic susceptibility and is repelled by a magnetic field?
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✅ C. Diamagnetic
Diamagnetic materials exhibit negative magnetic susceptibility and are weakly repelled by external magnetic fields because their orbital electrons create induced magnetic fields opposing the applied field. In contrast, ferromagnetic materials like iron show strong positive susceptibility and are strongly attracted. This fundamental magnetic property is tested in examinations alongside paramagnetic and ferrimagnetic classifications.
Question page →Question 17Easy
Which instrument is used to measure humidity or moisture content in the atmosphere?
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✅ B. Hygrometer
A hygrometer is the standard scientific instrument specifically designed to measure the moisture content or relative humidity present in the atmosphere. Alternative instruments like the barometer measure atmospheric pressure, whereas the hydrometer is used to determine the specific gravity or relative density of liquids rather than atmospheric water vapor.
Question page →Question 18Hard
What is the angular frequency of oscillation of a simple pendulum of length L located in a region where the acceleration due to gravity is g?
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✅ A. Square root of g over L
The restoring torque acting on a simple pendulum for small angular displacements leads to a differential equation of simple harmonic motion whose angular frequency omega equals the square root of g divided by L. The time period of oscillation is inversely proportional to this angular frequency. This relationship allows precise determination of local gravitational acceleration in geophysics.
Question page →Question 19Medium
In the context of thermodynamics and heat transfer, which statement accurately distinguishes between thermal conduction and thermal convection?
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✅ A. Conduction involves molecular vibration without net mass transfer, whereas convection involves actual bulk movement of fluid matter
Thermal conduction transfers energy through molecular collisions and lattice vibrations without bulk displacement of the medium, while convection requires fluid flow where warm portions rise and cooler portions sink. Conduction does not require fluids and convection cannot operate in empty vacuums without matter. Radiation handles electromagnetic infrared transfer rather than conduction or convection. Metals excel at conduction due to free electrons, whereas liquids and gases primarily transfer heat via convection currents. Gradients in temperature drive both modes of thermal energy transport.
Question page →Question 20Easy
What is the name of the device used to step up or step down alternating voltage based on mutual induction?
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✅ C. Transformer
A transformer operates on the principle of electromagnetic induction between multiple coils to alter alternating voltage levels efficiently without changing frequency. Devices like electric motors convert electrical energy into mechanical energy, whereas generators perform the reverse conversion. Power transmission grids rely heavily on step-up transformers to minimize resistive energy losses over long distances. Faraday's law of induction forms the theoretical underpinning for all transformer designs.
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