What is the absolute refractive index of kerosene?
1.44
Understanding Absolute Refractive Index of Kerosene
The question asks about the absolute refractive index of kerosene. The refractive index of a material is a measure of how much the speed of light changes when it enters that material from a vacuum. The absolute refractive index specifically compares the speed of light in a vacuum to the speed of light in the given medium.
The formula for absolute refractive index ($\mu$ or $n$) is:
\( \mu = \frac{\text{Speed of light in vacuum (c)}}{\text{Speed of light in medium (v)}} \)
Since the speed of light in a vacuum ($c$) is the maximum speed possible, the absolute refractive index of any medium is always greater than 1.
What is the Absolute Refractive Index of Kerosene?
Different materials have different refractive indices. These values are typically determined experimentally. The absolute refractive index of kerosene is a known physical property.
Based on standard physics data, the absolute refractive index of kerosene is approximately 1.44.
Let's look at the options provided:
- 1.46
- 1.31
- 1.47
- 1.44
Comparing the known value with the given options, 1.44 matches the standard absolute refractive index of kerosene.
Comparing Refractive Indices of Common Materials
To provide context, here is a table showing the approximate absolute refractive indices of some common substances:
| Material | Absolute Refractive Index ($\mu$) |
|---|---|
| Vacuum | 1.000 |
| Air | 1.0003 |
| Water | 1.33 |
| Alcohol | 1.36 |
| Kerosene | 1.44 |
| Crown Glass | 1.52 |
| Diamond | 2.42 |
This table shows that the absolute refractive index of kerosene is indeed around 1.44, making option 4 the correct answer.
Why Other Options are Incorrect
- 1.46: This value is close but not the standard absolute refractive index for kerosene. It might be the refractive index of another substance or a slightly different grade/mixture.
- 1.31: This value is too low for kerosene. It is closer to the refractive index of materials like ice (approx 1.31) or slightly less dense substances.
- 1.47: This value is slightly higher than the standard absolute refractive index for kerosene. It is closer to the refractive index of materials like flint glass (approx 1.65) or carbon disulfide (approx 1.63).
Therefore, based on standard optical properties, the absolute refractive index of kerosene is 1.44.
Revision Table: Key Refractive Index Concepts
| Concept | Definition | Formula |
|---|---|---|
| Absolute Refractive Index ($\mu$) | Ratio of the speed of light in vacuum to the speed of light in the medium. | \( \mu = \frac{c}{v} \) |
| Relative Refractive Index ($\mu_{21}$) | Ratio of the speed of light in medium 1 to the speed of light in medium 2. Also, ratio of absolute refractive index of medium 2 to medium 1. | \( \mu_{21} = \frac{v_1}{v_2} = \frac{\mu_2}{\mu_1} \) |
| Snell's Law | Relates the angles of incidence and refraction to the refractive indices of the two media. | \( \mu_1 \sin \theta_1 = \mu_2 \sin \theta_2 \) |
Additional Information: Factors Affecting Refractive Index
While the absolute refractive index of a substance like kerosene is often given as a single value, it's important to know that the refractive index can vary slightly depending on certain factors:
- Wavelength of Light: The refractive index is generally different for different colors (wavelengths) of light. This phenomenon is called dispersion, which is why a prism splits white light into its constituent colors. The value 1.44 is typically for a specific wavelength, often the yellow sodium D-line.
- Temperature: The density of a material changes with temperature, which can slightly affect its refractive index.
- Pressure: For gases, refractive index is significantly affected by pressure due to changes in density. For liquids like kerosene, the effect is less pronounced but still exists.
Understanding the absolute refractive index of kerosene and other materials is fundamental in studying optics, particularly in topics like refraction, lenses, and prisms.
Important Questions from Polarization by Reflection
The refractive index of water \(_a\mu_w=\frac{4}{3}\) and refractive index of glass \(_a\mu_g=\frac{3}{2}\) . A lens placed in air has focal length 10 cm. What will be its focal length if placed inside water?
The refractive index of water and dense flint glass are 1.33 and 1.65, respectively. A ray of light travels from dense flint glass to water. The refractive index of water with respect to dense flint glass is _______ and the light ray bends _______ the normal in water.
The refractive indices of quartz crystal for right handed and left handed circularly polarized light of wavelength 762.9 nm are 1.5391 and 1.5392 respectively. The angle of rotation produced by the crystal plate of thickness 0.5 mm is:
A ray of light is incident on a transparent medium at an angle of 60°. The reflected ray of light is found to be completely polarised. Then, the refractive index of the transparent medium is nearly:
For which of the following media is the absolute refractive index almost equal to one?
