Absolute Refractive Index Definition Explained
The absolute refractive index of a medium is a fundamental concept in optics. It quantifies how much light slows down when it passes through that medium compared to its speed in a vacuum.
Understanding the Definition
Specifically, the absolute refractive index is defined as the ratio between two speeds:
- The speed of light in a vacuum (denoted by c).
- The speed of light in the specific medium (denoted by v).
Mathematical Representation
This relationship is expressed by the following formula:
$ n = \frac{c}{v} $
Where:
- n represents the absolute refractive index of the medium.
- c is the speed of light in a vacuum, approximately $3 \times 10^8$ meters per second.
- v is the speed of light in the medium.
Since the speed of light in any medium (v) is always less than the speed of light in a vacuum (c), the absolute refractive index (n) is always greater than 1.
Analyzing the Options
Based on the definition:
- Option 1: medium; vacuum - This represents the ratio $\frac{v}{c}$, which is the inverse of the absolute refractive index.
- Option 2: medium; air - The speed of light in air is very close to the speed of light in a vacuum. The ratio of speed of light in a medium to speed of light in air defines the *relative* refractive index (when air is the reference medium), not the absolute refractive index.
- Option 3: vacuum; medium - This represents the ratio $\frac{c}{v}$, which correctly matches the definition of the absolute refractive index.
- Option 4: air; medium - Similar to Option 2, this uses air as the reference, not vacuum.
Therefore, the absolute refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in the medium.
Important Questions from Basic Concepts in Physics
$50 \ \Omega$, $50 \ \Omega$ and $100 \ \Omega$ resistors are connected in series in a circuit. They can be replaced with a single resistor of ______________in the circuit.
- Which of the following statements correctly describes the relationship among the incident ray, the refracted ray, and the normal at the point of incidence when light passes from one transparent medium to another?
- Given below are two statements. Select the correct answer from the options given for these statements.
Statement I: Particles of matter are continuously moving, that is, they possess what we call kinetic energy.
Statement II: With increase in temperature, the kinetic energy of the particles also increases. - Which of the following statements are correct?
(i) Melting point indicates the strength of forces of attraction between particles.
(ii) During melting, temperature of the solid remains constant until it has completely melted.
(iii) Boiling is a surface phenomenon.
(iv) Steam at 373 K has more energy than water at 373 K. - Which of the following is NOT true about the Universal Law of Gravitation?
