Newtons ring Experiment

Summary

This video covers the Newton's Rings experiment, demonstrating interference patterns in reflected light. It explores the setup and components required for the experiment, such as the sodium lamp, glass plate, plano-convex lens, and traveling microscope. The video explains how interference leads to circular fringes, with dark spots at the center, and goes on to detail methods for calculating the radius of bright and dark rings. Applications of the experiment, such as determining the refractive index, thickness of wires, wavelength of light, and testing optical flatness, are also discussed, showcasing its significance in real-world physics and technology.

Takeaways

• 😀 Newton's Ring Experiment is based on interference of light in reflected light, and was first observed by Sir Isaac Newton.
• 😀 The experiment uses a sodium lamp, a glass plate at a 45° angle, and a plano-convex lens to create an interference pattern.
• 😀 Interference fringes observed in the Newton's Ring experiment are circular due to varying air film thickness between the lens and glass plate.
• 😀 At the center of the interference pattern, a dark spot is observed due to destructive interference caused by phase change during reflection.
• 😀 The interference fringes are called 'fringes of equal thickness', resulting from alternating maxima and minima due to film thickness variation.
• 😀 The diameter of the rings in the Newton’s Ring pattern can be determined mathematically using the interference conditions for constructive and destructive interference.
• 😀 The radius of the dark rings is proportional to the square root of the natural numbers, and similarly, the radius of bright rings follows a proportional pattern.
• 😀 Applications of the Newton's Ring experiment include determining the wavelength of light, refractive index of liquids, testing optical flatness, and producing anti-reflection coatings.
• 😀 The wavelength of light can be determined by calculating the diameter differences between dark rings using a specific formula derived from the interference pattern.
• 😀 The refractive index of a liquid can be calculated by replacing the air medium with the liquid medium in the experiment, using the difference in diameters of rings observed in both media.
• 😀 Anti-reflection coatings are based on the principle of thin film interference, reducing glare and improving clarity, commonly used in optical lenses, telescopes, and cameras.

Q & A

What is the primary topic discussed in the video?

The primary topic discussed is Newton's Ring Experiment, focusing on interference patterns and their applications in optics.

What are some of the applications of the Newton's Ring Experiment?

Applications of the Newton's Ring Experiment include determining the thickness of a wire, refractive index, wavelength of incident light, radius of curvature of lenses, testing the surface flatness, and creating anti-reflection films.

What is the purpose of the Newton's Ring Experiment?

The purpose of the Newton's Ring Experiment is to observe interference patterns created by reflected light, which helps in determining certain physical properties like wavelength, refractive index, and radius of curvature.

Who first observed the Newton's Ring Experiment?

The Newton's Ring Experiment was first observed by Sir Isaac Newton.

What is the construction setup for the Newton's Ring Experiment?

The setup includes a sodium vapor lamp as the light source, a glass plate inclined at 45 degrees, a plano-convex lens, a thin air film between the lens and the glass plate, and a traveling microscope to observe the interference pattern.

Why are the fringes in the Newton's Ring pattern circular?

The fringes are circular due to the variation in the thickness of the air film between the plano-convex lens and the glass plate. The thickness increases as you move outward, and the points with the same thickness form concentric circles.

Why is there a dark spot at the center of the Newton's Ring pattern?

The dark spot at the center occurs due to destructive interference, as the film thickness at the center is very small, leading to phase changes that cancel out the reflected waves.

How can the radius of the dark and bright rings in the Newton's Ring pattern be determined?

The radius of the dark rings can be calculated using the formula r_m = √(M * λ * R), where M is the fringe number, λ is the wavelength of light, and R is the radius of curvature of the lens. For bright rings, the formula r_m = √((2M + 1) * λ * R) is used.

How is the wavelength of light determined using the Newton's Ring experiment?

The wavelength of light can be determined by measuring the diameter differences of rings and using the formula λ = (d²_m+P - d²_m) / (4pR), where d is the diameter, p is the distance between two diameters, and R is the radius of curvature.

What is the role of the refractive index in the Newton's Ring experiment when using a liquid medium?

When a liquid medium is used, the refractive index (μ) alters the interference conditions. The formula for the diameter of the rings becomes d_m = (4 * M * λ * R) / μ. By comparing the diameter differences in air and liquid, the refractive index of the liquid can be calculated.