# About thin film (max bright/dark)

• kenok1216
In summary, the conversation discusses the relationship between the thickness of SiO2 as a thin film and the wavelength of light. It is noted that the reflected light experiences a 180 degree phase change when entering SiO2 and Si. The equations for dark and bright fringes are given and it is mentioned that the thickness t of SiO2 changes as it is a wedge. The question of how many wavelengths of light thick the widest part of the wedge is and the definition of "t" are also brought up. Finally, it is mentioned that the SiO2 thickness changes as a wedge and that a bright strip is seen when the condition 2nt = mλ is met. The question of how thick the SiO2 wedge is

## The Attempt at a Solution

SiO2 as the thin film,when light entry SiO2 and Si then the reflected light has 180 phase change,
for dark fringes
2nt=(m+1/2)λ
for bright fringes
2nt=mλ
for dectect max of bright/dark,-1<=sinx<=1, then no idea to prove father[/B]

Relate the thickness of the wedge to the wavelength of light ... notice there are seven fringes, so how many wavelengths of light thick is the widest part of the wedge?

Simon Bridge said:
Relate the thickness of the wedge to the wavelength of light ... notice there are seven fringes, so how many wavelengths of light thick is the widest part of the wedge?
could you possibly explain more? still not understand..

kenok1216 said:

## The Attempt at a Solution

SiO2 as the thin film,when light entry SiO2 and Si then the reflected light has 180 phase change,
for dark fringes
2nt=(m+1/2)λ
for bright fringes
2nt=mλ[/B]
Do you know what "t"means?
How thick is the oxide at the thinnest part?

ehild said:
Do you know what "t"means?
How thick is the oxide at the thinnest part?
t=the thick of SiO2

kenok1216 said:
t=the thick of SiO2
The SiO2 thickness changes, as it is a wedge. You see a bright strip where the thickness t matches the condition 2nt = mλ.
How thick is the SiO2 wedge at the thinnest part? Do you see it bright or dark?

## What is a thin film?

A thin film is a layer of material that is only a few nanometers to microns in thickness. It can be made from a variety of materials such as metals, oxides, or polymers.

## How does thin film affect brightness?

The thickness and composition of a thin film can affect its optical properties, including brightness. For example, a thin film with a high refractive index will reflect more light and appear brighter.

## What is meant by "max bright" in relation to thin film?

"Max bright" refers to the maximum amount of light that can be reflected or transmitted through a thin film. This is typically achieved when the thin film is at a specific thickness and composition.

## How does thin film affect darkness?

The thickness and composition of a thin film can also affect its ability to absorb light, which can impact darkness. For example, a thin film with a low refractive index will absorb more light and appear darker.

## What factors can influence the brightness and darkness of a thin film?

The optical properties of a thin film, such as its thickness, composition, and refractive index, can influence its brightness and darkness. Other factors that can affect these properties include the angle of incident light, the type of light source, and the surface roughness of the thin film.