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).
Difference Between Speed and Velocity
Speed is scalar (distance/time); velocity is vector (displacement/time). Speed is always positive; velocity can be negative. Average speed ≥ average velocity.
Difference Between Tungsten and Nichrome
Tungsten: pure metal, mp 3422°C, used in bulb filaments. Nichrome: Ni-Cr alloy, high resistivity 110×10⁻⁸ Ω·m, used in heating elements. Key differences explained.
What is the Least Count of a Digital Vernier Caliper?
Learn the least count of a digital vernier caliper. Understand how accurate it is (0.01 mm) compared to a manual caliper and how it works.
Dimensional Formula of Acceleration
Learn how to derive the dimensional formula of acceleration [M0 L1 T-2]. Step-by-step physics derivation using velocity and time.
Dimensional Formula of Angular Momentum — [ML²T⁻¹]
Dimensional formula of angular momentum is [ML²T⁻¹]. Derived from L = mvr or L = Iω. SI unit: kg·m²/s or J·s. Derivation with steps and explanation.
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