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Physics Optics Mechanics MCQs
High-yield multiple choice questions asked in previous years (UPSC, SSC CGL, JKSSB, RRB & State PSCs).
High-Yield Concept Capsule & Key Facts
📌 Core physical science questions in SSC CGL, NDA, CDS, and State PSCs.
Newtonian Mechanics & Gravitation Principles
- • Newton's Laws of Motion: 1st Law (Inertia - qualitative definition of force); 2nd Law (Rate of change of momentum is proportional to applied force, F = ma); 3rd Law (Every action has an equal and opposite reaction).
- • Universal Gravitation: F = G(m1×m2)/r^2 (G = 6.674 × 10^-11 N m^2/kg^2, measured by Cavendish). Acceleration due to gravity (g = 9.8 m/s^2 on Earth's surface). Value of 'g' is maximum at poles and minimum at the equator; zero at Earth's center.
- • Escape Velocity: Minimum velocity required to escape Earth's gravitational pull: v_e = sqrt(2gR) ≈ 11.2 km/s on Earth (approx 2.4 km/s on the Moon, explaining absence of lunar atmosphere).
- • Archimedes' Principle & Surface Tension: Upward buoyant force equals weight of displaced fluid. Surface tension causes spherical shape of liquid raindrops and capillary action.
Optics, Wave Phenomena & Vision Defects
- • Reflection & Refraction: Snell's Law (sin i / sin r = constant). Total Internal Reflection (TIR): Occurs when light travels from denser to rarer medium at an angle greater than the critical angle. Applications: Optical fibers, mirages in deserts, sparkling of diamonds, endoscopy.
- • Dispersion & Scattering: White light dispersed by prism into VIBGYOR (Red bends least / longest wavelength; Violet bends most / shortest). Rayleigh Scattering: Scattering intensity inversely proportional to wavelength^4. Explains blue sky and red sunset.
- • Human Vision Defects: Myopia (Near-sightedness - image formed in front of retina, corrected by Concave lens); Hypermetropia (Far-sightedness - image formed behind retina, corrected by Convex lens); Presbyopia (old-age loss of accommodation, corrected by Bifocal lens); Astigmatism (uneven cornea curvature, corrected by Cylindrical lens).
| Physical Phenomenon | Core Scientific Principle | Key Formula / Constant | Practical Real-World Application |
|---|---|---|---|
| Optical Fiber | Total Internal Reflection (TIR) | Angle of incidence > Critical angle | High-speed broadband telecommunications |
| Blue Color of Sky | Rayleigh Scattering | Scattering ~ 1 / lambda^4 | Shorter blue wavelengths scattered most |
| Myopia Correction | Diverging concave lens | Power P = 1 / f (Diopters) | Extends focal point onto retina |
| Escape Velocity | Gravitational escape | v_e = sqrt(2gR) = 11.2 km/s | Rocket propulsion and satellite launch |
| Raindrop Spherical Shape | Surface Tension | Minimizes surface area | Cohesive molecular attraction in water |
| Mirage in Deserts | Total Internal Reflection | Temperature gradient in air | Illusion of water pools on hot roads |
Showing 15 Practice Questions
Q1SSC CGL 2023Easy
Which physical principle explains the transmission of high-speed digital light signals through optical fiber cables?
Q2UPSC CSE PrelimsEasy
The apparent blue color of the clear daytime sky is caused by which optical phenomenon?
Q3JKSSB FAA 2022Easy
Which type of corrective lens is prescribed by optometrists to correct Myopia (near-sightedness)?
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Q4CDS 2022Easy
What is the escape velocity of a projectile fired from the surface of the Earth?
Q5JKSSB VLW 2023Easy
Why do small liquid raindrops naturally assume a spherical shape?
Q6SSC CGL Tier-1Easy
The acceleration due to gravity (g) on the surface of the Earth is:
Q7JKPSC KAS PrelimsMedium
When a ship floats from freshwater river water into denser saline sea water, it:
Q8NDA 2022Easy
Which color of the visible spectrum undergoes the MAXIMUM deviation (bending) when white light passes through a glass prism?
Q9SSC CHSLEasy
The sparkling and brilliance of a cut diamond is primarily attributable to:
Q10JKSSB Sub-InspectorEasy
What is the SI unit of measurement for the optical power of a lens?
Q11UPSC CSE PrelimsEasy
A hydraulic lift or hydraulic car brake operates in direct accordance with which fundamental physical law?
Q12JKSSB Patwari 2024Medium
Why does a stationary astronaut experience weightlessness while orbiting Earth inside the International Space Station (ISS)?
Q13CDS 2021Easy
An optical device known as a 'Periscope', used in submerged submarines to observe surface targets, relies on two plane mirrors inclined at an angle of:
Q14SSC CGLEasy
Which of Newton's laws of motion provides the quantitative mathematical formula for calculating Force (F = ma)?
Q15JKSSB Junior AssistantEasy
The twinkling of stars at night is caused by:
Frequently Asked Questions (Physics Optics Mechanics)
Q: What is Total Internal Reflection (TIR) and what conditions are required for it to occur?
Total Internal Reflection occurs when a ray of light travelling from an optically denser medium to an optically rarer medium strikes the boundary at an angle of incidence greater than the critical angle, reflecting 100% of the light back into the denser medium. It is the operating principle behind fiber optic cables, medical endoscopes, and sparkling diamonds.
Q: Why does a clear sky appear blue during the daytime?
According to Rayleigh's Scattering Law, the intensity of scattered light is inversely proportional to the fourth power of its wavelength. Because blue and violet light have much shorter wavelengths than red light, they are scattered in all directions by nitrogen and oxygen molecules in the upper atmosphere far more intensely than other colors.
Q: Which corrective optical lens is used to treat Myopia (near-sightedness)?
Myopia (where rays from distant objects converge and focus in front of the retina) is corrected using a Concave (diverging) lens, which diverges incoming parallel light rays so they focus sharply onto the retina.
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