Practice Physics MCQ Questions 1–25 out of 43. Free quiz with answers and explanations for UPSC, SSC, Railway exam preparation. Strengthen your general science fundamentals with our technical Physics GK quiz. Practice high-frequency multiple-choice questions on mechanics, thermodynamics, light, optics, electricity, magnetism, and modern atomic physics tailored perfectly to meet the syllabus requirements of SSC, RRB NTPC, and NDA.
What is the speed of light in a vacuum, which serves as the universal speed limit?
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Explanation
The speed of light in a vacuum is approximately 299,792 kilometers per second (usually rounded to 3 x 10^8 m/s or 300,000 km/s). [Memory Trick: Imagine driving a car across the world '3 lakhs' (300,000) times in one eye-blink!]
2
What physical quantity is measured in the SI unit 'Watt' (named after progress inventor James Watt)?
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Explanation
Power is the rate at which work is done or energy is transferred, measured in Watts (Joules per second). [Memory Trick: Powerful people can pull a high-voltage bulb's 'Watt' to light up their ideas!]
3
Which principle states that an object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces?
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Explanation
Archimedes' Principle explains buoyancy and flotation. According to legend, Archimedes discovered this while taking a bath and ran naked shouting 'Eureka!'. [Memory Trick: 'Archimedes' took a dip in a tub, displacing water, and made 'floating' possible.]
4
Which optical phenomenon is primarily responsible for the propagation of light signals through fiber optic cables?
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Explanation
Total Internal Reflection occurs when light traveling through a denser medium hits a boundary at an angle larger than the critical angle, bouncing entirely back inside. [Memory Trick: In fiber optics, light is locked in a 'Total' trap where it only 'Reflects' 'Internally'.]
5
Albert Einstein was awarded the 1921 Nobel Prize in Physics for his explanation of which phenomenon?
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Explanation
Einstein won the Nobel Prize specifically for describing the photoelectric effect, showing light acts as packets of energy (photons), which laid foundations for quantum mechanics. [Memory Trick: Light hits a metal 'photo' plate to push out 'electrons' = 'Photoelectric' effect.]
6
Where is the acceleration due to gravity (g) strongest on the surface of the Earth?
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Explanation
Because Earth is an oblate spheroid (flattened at poles, bulging at equator), the poles are closer to Earth's center of mass, making gravity 'g' strongest there (~9.83 m/s²). [Memory Trick: North and South 'Poles' pull you down like heavy magnetic bars.]
7
Sound waves cannot travel through which of the following mediums?
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Explanation
Sound is a mechanical wave requiring a material medium (solid, liquid, or gas) to propagate through compression and rarefaction. It cannot travel through a vacuum. [Memory Trick: In space (a vacuum), nobody can hear you scream!]
8
Which type of wave scattering is responsible for giving the clear daytime sky its characteristic blue color?
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Explanation
Rayleigh scattering states that shorter wavelengths (blue/violet) of light scatter much more off small air molecules than longer wavelengths (red). [Memory Trick: 'Ray' (light) behaves in a lovely 'Rayleigh' blue style in the atmosphere.]
9
What is the SI unit of electrical resistance, representing the opposition to current flow?
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Explanation
Resistance is measured in Ohms (denoted by Ω), named after German physicist Georg Simon Ohm. State relation: V = IR. [Memory Trick: In meditation, chanting 'Ohm' creates inner peace and 'resists' external distractions.]
10
Who is credited with the discovery of natural radioactivity in 1896 while working with uranium salts?
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Explanation
French physicist Henri Becquerel discovered radioactivity in 1896 when he noticed uranium emission fogged photographic plates even in the dark. [Memory Trick: 'Becquerel' discovered radiation from 'uranium' like a 'baking' heater.]
11
Which region of the electromagnetic spectrum possesses the shortest wavelength and highest frequency of all?
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Explanation
Gamma rays have the highest energy, highest frequency, and shortest wavelengths in the EM spectrum, emitting from nuclear decay. [Memory Trick: Marvel's Hulk was hit by highly packed 'Gamma' rays which made him extremely powerful.]
12
What type of spherical mirror is used as a rear-view mirror in vehicles to provide a wider field of view?
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Explanation
A convex mirror diverges light rays and forms diminished, erect virtual images, allowing drivers to view a vast portion of traffic behind them. [Memory Trick: Convex curves out ('veX' looks like a shield), pushing a wide-angle view into your eyes.]
13
What is the value of 'Absolute Zero' on the Celsius temperature scale, at which thermodynamic motion stops?
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Explanation
Absolute zero is defined as 0 Kelvin, which equates to exactly -273.15 °C on the Celsius scale. [Memory Trick: Thermometers freeze 'absolutely' down to '-273' below!]
14
Which nuclear process serves as the core energetic power source of our Sun and other stars?
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Explanation
Nuclear fusion is the process where light hydrogen atomic nuclei fuse under massive heat and gravity to form helium, releasing vast solar energy. [Memory Trick: 'Fu-sion' is 'Fusing' (combining) things together to make a giant sun.]
15
What is the minimum speed needed (Escape Velocity) to leave Earth's gravitational field and enter space?
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Explanation
The escape velocity of any object from Earth's gravity is roughly 11.2 km/s (or about 25,000 mph). [Memory Trick: Imagine escaping in '1st' gear and hitting a speed of '1.2' sound speeds = 11.2 km/s!]
16
Which force pulls falling objects towards a constant speed, known as terminal velocity, countering gravitational pull?
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Explanation
As speed increases, air resistance increases. When drag equals gravitational force, acceleration becomes zero, and the object falls at terminal velocity. [Memory Trick: The air acts like a 'braking' blanket = 'Air Resistance'.]
17
What is the direction of the centripetal force acting on an object executing uniform circular motion?
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Explanation
Centripetal force means 'center-seeking' force, which always acts perpendicular to velocity, directed towards the center of rotation. [Memory Trick: 'Centri-petal' -> 'Petal' falls inward to the 'Center' of the flower.]
18
In semiconductor physics, what is the majority charge carrier in a P-type semiconductor?
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Explanation
P-type semiconductors are doped with trivalent impurities (like Boron), creating electron vacancies called 'holes' that act as positive charge carriers. [Memory Trick: 'P'-type stands for 'Positive', which are 'Holes' looking to receive negative electrons.]
19
The acronym 'LASER' stands for 'Light Amplification by' which of the following physical processes?
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Explanation
LASER stands for 'Light Amplification by Stimulated Emission of Radiation'. It produces coherent, monochromatic, and collimated beam lasers. [Memory Trick: Photons are 'Stimulated' (excited) together to march in a straight laser line.]
20
What is the phenomenon where a superconducting material completely expels magnetic fields from its interior when cooled below its critical temperature?
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Explanation
The Meissner effect is a characteristic hallmark of superconductors. It expels magnetic flux, allowing magnets to float in mid-air above them (quantum levitation). [Memory Trick: Superconductor says 'Mind your business' and 'Messes up' (Meissner) the magnetic fields, ejecting them completely!]
21
Who discovered electromagnetic induction in 1831, demonstrating that a moving magnetic field induces an electric current?
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Explanation
Michael Faraday discovered electromagnetic induction, inventing the generator. This principle is used in transformers, generators, and induction hobs. [Memory Trick: 'Faraday' moved a magnet far 'away' and close to a coil to make current 'fare' (flow).]
22
The First Law of Thermodynamics is essentially a restatement of which fundamental physical law?
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Explanation
The First Law of Thermodynamics states that heat added is equal to work done plus increase in internal energy ($Q = W + \Delta U$), keeping total energy conserved. [Memory Trick: Energy can change form, but never disappear. '1st' rule of cosmos = preserve energy.]
23
What cohesive fluid property allows insects like pond skaters to walk on water without sinking?
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Explanation
Surface tension is caused by cohesive forces between water molecules at the interface, forming an elastic-like membrane sheet. [Memory Trick: The 'Surface' of water stretches with 'Tension' like a trampoline for bugs.]
24
Which physics theorem explains how airplane wings generate lift due to fluid velocity differences?
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Explanation
Bernoulli's principle states that an increase in fluid speed happens simultaneously with a decrease in pressure. Air travels faster over the curved wing top, creating lower pressure and upward lift. [Memory Trick: Burn a candle, blow air over it, the flame rises = 'Bernoulli' rises.]
25
By which thermodynamic mechanism does solar heat from the Sun traverse the vacuum of space to reach Earth?
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Explanation
Radiation is heat transfer via electromagnetic waves (like infrared), requiring no solid or fluid medium to travel. [Memory Trick: Solar rays 'radiate' directly through cosmic darkness to warm our skins.]