Nothing in the entire universe can travel faster than light. In Physics, knowing the exact speed of light is essential for solving numerical problems in the 'Reflection and Refraction' chapters.
Symbol: Denoted by 'c'.
Speed in Vacuum/Air: $3 \times 10^8$ m/s (3,000,000 km/sec).
Fact: Light from the Sun takes approximately 8 minutes and 20 seconds to travel through space and reach Earth.
Light travels fastest when there is absolutely nothing blocking its path (in a perfect vacuum, like outer space).
When light enters the Earth's atmosphere, it bumps into air molecules, which slows it down very, very slightly.
When light enters denser mediums, it slows down significantly:
The speed of light in air is slightly less than in a vacuum, but for all practical and mathematical purposes, it is considered to be exactly $3 \times 10^8$ meters per second (3 lakh km/s).
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A planet moving around a star follows Kepler's laws. Gravitational force provides centripetal force. T² ∝ R³ (Kepler's third law). Learn orbital speed and period.
Applications of Gauss's Law in Electrostatics
Learn the main applications of Gauss's theorem in electrostatics. Calculate electric fields for infinitely long wires, infinite plane sheets, and spherical shells.
A Proton Moves Along Horizontal Line and Towards Observer — Direction of Magnetic Field
When a proton moves along a horizontal line towards the observer, the magnetic field lines form anticlockwise circles around its path, by the right-hand rule.
A Siren Blown in a Workshop — Sound Waves, Doppler Effect, and Safety
When a siren is blown in a workshop, it produces sound waves. If the siren moves, the Doppler effect causes frequency change. Sound travels at 343 m/s in air.
Atmospheric Refraction — Definition and Natural Phenomena
What is atmospheric refraction? Learn how the bending of light by Earth's atmosphere causes the twinkling of stars and early sunrise. Class 10 Science.
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