Michelson Interferometer - Part 1 | Construction and find Wavelength | explained in HINDI

EduPoint

21 Jul 201711:53

Summary

TLDRThe video script discusses the concept of interference, specifically focusing on the use of monochromatic light and its applications. It explains how to determine the wavelength of light using a monochromatic source and a device called an interferometer. The script also covers basic applications like measuring the thickness and refractive index of a transparent material. The video explains the construction and working of the interferometer, the generation of light waves, and their behavior when interacting with mirrors and a glass slab. It further delves into the interference pattern formation on a screen, the effect of rotating a knob to alter the pattern, and the principles behind constructive and destructive interference. The script concludes by hinting at future discussions on calculating the wavelength of monochromatic light sources.

Takeaways

🔬 The discussion focuses on the interference phenomenon and its basic applications, particularly determining the wavelength of monochromatic light.
🔭 Applications include measuring the thickness and refractive index of a thin transparent material, as well as the refractive index of a gas.
📡 The construction of the interferometer is described, which includes a monochromatic light source, a lens, a glass slab, and two mirrors (m1 and m2).
🌟 Light from the source passes through the lens, reflects off the mirrors, and interferes upon returning to the screen, creating a pattern of fringes.
🔄 Rotating a knob adjusts the position of the mirrors, which affects the interference pattern visible on the screen, causing the fringes to expand or contract.
🔍 The concept of constructive and destructive interference is explained, depending on the path difference between the light waves.
📏 The path difference is crucial in determining the interference pattern, and it is directly related to the distance the mirrors move.
🔄 As the mirrors move, the phase difference between the light waves changes, shifting the interference pattern from constructive to destructive and vice versa.
📉 The pattern of fringes on the screen changes as the mirrors are adjusted, with fringes appearing to move towards or away from the center.
⏱️ The video concludes with a discussion on how the number of 'cross-overs' in the interference pattern can be used to calculate the wavelength of the monochromatic light source.

Q & A

What is the basic application of interference discussed in the script?
-The basic application of interference discussed is determining the wavelength of monochromatic light by using a monochromatic light source.
How can we find the thickness and refractive index of a thin transparent material using interference?
-By analyzing the interference pattern produced when light passes through a thin transparent material, one can determine its thickness and refractive index.
What is the role of mirrors in the interference experiment described in the script?
-Mirrors in the experiment are used to reflect light waves, which then interfere with each other to create an interference pattern on a screen.
Why does the interference pattern change when the knob is rotated in the experiment?
-Rotating the knob changes the path difference between the two light waves, which in turn alters the interference pattern observed on the screen.
What is the significance of the term 'web length' in the context of the script?
-The 'web length' refers to the path difference introduced by the optical setup, which is crucial for the interference pattern formation.
How does the movement of the mirror affect the interference pattern in terms of path difference?
-Moving the mirror changes the path difference between the two light waves, which can lead to constructive or destructive interference, depending on whether the path difference is an integer multiple of the wavelength or not.
What happens when the phase difference between the two light waves is 180 degrees?
-When the phase difference between the two light waves is 180 degrees, destructive interference occurs, leading to a dark fringe in the interference pattern.
What is the relationship between the fringes observed on the screen and the path difference?
-The fringes observed on the screen correspond to different path differences between the interfering light waves, with constructive interference occurring at integer multiples of the wavelength and destructive interference at odd multiples of half the wavelength.
How can the wavelength of monochromatic light be determined from the interference pattern?
-By counting the number of times the interference pattern repeats (cross-overs) and knowing the path difference introduced by the optical setup, one can calculate the wavelength of the monochromatic light using the formula that relates path difference to the wavelength.
What is the purpose of rotating the knob in the experiment?
-Rotating the knob in the experiment is used to adjust the path difference between the two light waves, which allows for the observation of how the interference pattern changes and ultimately helps in determining the wavelength of light.
What is the term used to describe the point where the central maximum of the interference pattern disappears?
-The term used to describe the point where the central maximum disappears is 'crossing over,' which signifies a change in the interference pattern due to the adjustment of the optical setup.

Outlines

00:00

🔬 Introduction to Interference and Basic Applications

The video begins with an introduction to Michael San and delves into the concept of interference, specifically focusing on monochromatic light sources. The basic applications discussed include determining the wavelength of light from a monochromatic source, understanding the principles of interferometry, and exploring the refractive index of thin transparent materials. The video aims to explain how to measure the wavelength of light using a monochromatic source and how to identify the refractive index of a material by observing interference patterns. The construction and working of the interferometer are also discussed, highlighting the role of mirrors and lenses in creating interference patterns on a screen. The video concludes with a demonstration of how adjusting a knob affects the interference pattern, illustrating the dependence of the pattern on the path difference between light waves.

05:01

🌈 Exploring Monochromatic Light and Constructive/Destructive Interference

This section of the video script discusses the properties of monochromatic light, using a red light source as an example. It explains how light waves from the source travel, reflect off mirrors, and interfere upon reaching a screen. The video elaborates on the concept of path difference and how it affects the interference pattern, either constructively or destructively. The script introduces the idea that a phase difference of 180 degrees (or odd multiples of 180 degrees) results in destructive interference, while no phase difference (or multiples of 360 degrees) leads to constructive interference. The video uses these principles to explain how rotating a knob in the setup changes the interference pattern on the screen, and how this change can be used to infer the wavelength of the monochromatic light source.

10:05

📏 Calculating Wavelength Using Interference Fringes

The final paragraph of the script focuses on the practical application of the principles discussed in the video. It introduces a method to calculate the wavelength of a monochromatic light source by observing the interference fringes on the screen and counting the number of 'cross-overs' as the knob is rotated. The video explains that each cross-over corresponds to a specific path difference, which is proportional to the wavelength of light. By counting the number of cross-overs and knowing the physical dimensions of the setup, one can calculate the wavelength. The script concludes by summarizing the method and encourages viewers to look forward to the next video for further exploration of these concepts.

Mindmap

Keywords

💡Interference

Interference in the context of the video refers to the superposition of light waves, resulting in a pattern of bright and dark fringes known as an interference pattern. This phenomenon is central to the video's theme as it is used to explain how the wavelength of light can be determined using a monochromatic light source. The script discusses how light waves from different paths interfere constructively or destructively, creating a pattern that can be analyzed to understand the properties of the light source.

💡Monochromatic Light

Monochromatic light is light that consists of a single wavelength or color. In the video, the importance of using a monochromatic light source for interference experiments is highlighted. It allows for a consistent and predictable interference pattern, which is essential for accurately measuring the wavelength of light. The script mentions using a monochromatic source to determine the wavelength by analyzing the interference pattern created when light passes through a slit and reflects off mirrors.

💡Wavelength

The wavelength is the distance between two consecutive peaks or troughs of a wave, such as a light wave. In the video, determining the wavelength of light is a key application of the interference experiment. The script describes how by adjusting the position of mirrors in the setup, the interference pattern changes, allowing for the calculation of the light's wavelength.

💡Transparent Material

A transparent material is one that allows light to pass through it with little to no scattering or absorption. In the video, the script mentions the use of a thin transparent material, such as a glass slab, to demonstrate how light interacts with different media. The thickness and refractive index of the material can affect the interference pattern, providing insights into the material's optical properties.

💡Refractive Index

The refractive index of a material is a measure of how much it slows down light as it passes through. In the video, the refractive index is discussed in relation to the transparent material used in the experiment. By analyzing the interference pattern and knowing the refractive index, one can determine the thickness of the material, which is an application of the principles discussed in the video.

💡Constructive Interference

Constructive interference occurs when two waves of the same frequency are in phase, resulting in a wave with a larger amplitude. In the video, constructive interference is mentioned as a condition where the path difference between two light waves is an integer multiple of the wavelength, leading to bright fringes in the interference pattern.

💡Destructive Interference

Destructive interference happens when two waves of the same frequency are out of phase, leading to a cancellation of the wave's amplitude. In the video, destructive interference is discussed as a condition where the path difference is an odd multiple of half the wavelength, resulting in dark fringes in the interference pattern.

💡Path Difference

Path difference refers to the difference in the optical path traveled by two light waves. In the video, the path difference is a critical factor in determining whether the interference is constructive or destructive. The script explains how changes in the path difference, by adjusting the mirrors, can shift the interference pattern on the screen.

💡Fringes

Fringes are the alternating bright and dark bands observed in an interference pattern. The video script describes how the adjustment of the setup, such as rotating a knob, changes the fringes' size and position, which is essential for understanding the relationship between the physical setup and the resulting interference pattern.

💡Mirrors

In the context of the video, mirrors are used to reflect light waves, creating a path difference necessary for interference patterns. The script describes a setup involving two mirrors (m1 and m2) that reflect light waves, which then interfere with each other after passing through a transparent material and a lens.

💡Screen

The screen in the video is where the interference pattern is observed. It captures the light that has passed through the setup, including the transparent material and been reflected by the mirrors. The script mentions how the interference pattern changes as the mirrors are adjusted, and the screen is crucial for visualizing these changes.

Highlights

Discussion on the basics of interference and its applications.

Explaining the simplest application of determining the wavelength of monochromatic light from a source.

Introduction to the concept of thin transparent materials and their refractive indices.

Explanation of how to measure the refractive index of a gas using standard meter and interference.

Introduction to the first video in the series focusing on the working and construction of the interferometer.

Description of the construction of the interferometer and the role of the light source and lens.

Explanation of light wave propagation through a glass slab and the phenomenon of internal reflection.

Discussion on the role of mirrors m1 and m2 in the interferometer setup.

Description of how light waves interfere on the screen and the formation of fringes.

Explanation of how rotating the nob affects the interference pattern and fringes on the screen.

The concept of constructive and destructive interference based on phase difference.

Understanding the path difference and its relation to wavelength in interference patterns.

The impact of mirror movement on the path difference and interference pattern.

Detailed explanation of how the interference pattern changes with the rotation of the nob.

The relationship between the number of crosses over in the interference pattern and the path difference.

Formula to calculate the wavelength of monochromatic light source using the path difference and number of crosses over.

Conclusion and预告 of the next video in the series.