Gelombang Cahaya / Optika Fisis • Part 5: Polarisasi Cahaya

Summary

This video tutorial covers the topic of light polarization in optics, focusing on various causes and effects, including reflection, refraction, double refraction, scattering, and selective absorption. The script explains key concepts such as Brewster's angle, how light interacts with different media, and the mathematical aspects behind polarization. It also walks through practical examples and problem-solving techniques involving polaroids and intensity changes, offering a clear understanding of how light is polarized and how these principles are applied in real-life scenarios. The tutorial is aimed at high school students studying physics, particularly those interested in optics.

Takeaways

• 😀 Polarization of light is the reduction of light intensity due to the loss of wave components.
• 😀 There are several causes of light polarization: reflection, refraction, double refraction, scattering, and selective absorption.
• 😀 Polarization can occur through reflection and refraction when light encounters the boundary between two mediums.
• 😀 Brewster's Law explains that when light is reflected and refracted at a specific angle (called the Brewster angle), the reflected light becomes completely polarized.
• 😀 The Brewster angle (IP) can be calculated using the formula: tan(IP) = N2 / N1, where N1 and N2 are the refractive indices of the two media.
• 😀 An example calculation showed that the refractive index of glass is √3, based on Brewster's Law and an incident angle of 60°.
• 😀 Double refraction happens when light passes through a material with double refraction properties (e.g., calcite), creating two separate light beams.
• 😀 The scattering of sunlight in the atmosphere, primarily due to particles, causes the blue sky we see, as blue light is scattered more than other colors.
• 😀 Selective absorption, in which polarizers are used to reduce light intensity and polarize light, is another method of light polarization.
• 😀 A real-world example showed how a setup of four polaroids, each rotated at 30°, results in a decrease in the light intensity passing through, which can be calculated using the intensity formula.
• 😀 The angle between polaroids affects the intensity of light that passes through, as seen in the case of polaroids arranged at specific angles to one another.

Q & A

What is the main topic of the video?

The video mainly discusses the topic of light waves and focuses on the polarization of light in physics, specifically in the context of high school-level science lessons.

What is polarization of light?

Polarization of light refers to the reduction in the intensity of light due to the removal of certain components of the light wave, often involving the alignment of light vibrations in a specific direction.

What are the main causes of light polarization mentioned in the video?

The main causes of light polarization mentioned are reflection and refraction, double refraction, scattering, and selective absorption.

How does reflection and refraction cause polarization of light?

When light strikes the boundary between two media with different refractive indices, part of the light is reflected and part is refracted. At a specific angle (Brewster's angle), the reflected light becomes fully polarized.

What is Brewster's Law?

Brewster's Law states that when light reflects off a surface at a specific angle (Brewster's angle), the reflected light will be completely polarized. The angle can be calculated using the formula: tan(θp) = n2 / n1, where θp is the polarization angle, and n1 and n2 are the refractive indices of the two media.

What is the significance of Brewster's angle in polarization?

Brewster's angle is the angle of incidence at which light reflecting off a surface is completely polarized. This angle results in the reflected and refracted light being perpendicular to each other.

What is double refraction and how does it cause polarization?

Double refraction occurs when light passes through a material with a double refractive index, splitting the light into two rays: an ordinary ray and an extraordinary ray. The extraordinary ray is polarized, leading to double images, as seen when light passes through a crystal like calcite.

What role does scattering play in light polarization?

Scattering causes polarization when sunlight interacts with dust particles in the atmosphere. The scattered light becomes polarized, which is why the sky appears blue, as blue light is scattered more effectively than other colors.

How does selective absorption lead to polarization?

Selective absorption occurs when a polarizing filter absorbs light waves that are oscillating in certain directions. This reduces the intensity of the light and results in polarized light being transmitted through the filter.

How does the arrangement of multiple polarizers affect light intensity?

When multiple polarizers are aligned at different angles, the intensity of light passing through decreases based on the angle between the polarizers. This relationship can be calculated using the formula I = I0 * cos²(θ), where I0 is the initial intensity, θ is the angle between the polarizers, and I is the transmitted light intensity.