Question about the color of a thin film

[Antoha1]

TL;DR

Color of thin film if monochromatic light is pointed against it

If monochromatic light is pointed directly at thin film, film's color can only vary in intensiveness of that particular color of light, because of interference. So, if light is pointed at it, so it is maximum or minimum or neither of interference. The color apeared can only be the color of light pointed (the same wavelength). If we start changing angle of direction of light pointed to the film, the color of the film changes from no color (minimum of interference) to the color pointed (maximum of interference) with no any other colors (wavelenghts) of light apeared. asking if this is correct. The space is fully isolated from any other light sources.

 

[Ibix]

Yes, ideally the brightnness of the reflection will vary and that's all. In reality, all sources have some bandwidth (they are not perfectly monochromatic), so in an actual experiment there would be some variation in reflected spectrum.

 

[renormalize]

TL;DR: Color of thin film if monochromatic light is pointed against it

Yes, your reasoning is correct. Take a look at: https://www.soapbubble.dk/en/articles/thin-film-interference which shows a half soap-bubble illuminated by a monochromatic sodium-vapor lamp of wavelength $589\,\text{nm}$:

 

[Gleb1964]

You need look to Haidinger fringes, fringes of equal inclination, formed with extended monochromatic source passing though the equal thickness film media. Interference fringes are localised at infinity.
Otherwise if the film thickness is variated, you can observe Newton fringes of equal thickness.

 

[sophiecentaur]

TL;DR: Color of thin film if monochromatic light is pointed against it

If monochromatic light is pointed directly at thin film, film's color can only vary in intensiveness of that particular color of light,

To avoid confusion, it would be better not to use the word "colour' in this sort of discussion the way light of different wavelengths is independent of what happens to other wavelengths. Because most visible 'colours' can be mimicked by mixtures of other monochromatic sources the result of interference processes could be inconclusive or difficult to report accurately. Stick to wavelength in all optics experiments except when actual colorimetry is involved.

 

[phyzguy]

In practice, you will see Newton's rings, even if the color of the light is monochromatic, as in these pictures in the Wikipedia entry.
https://en.wikipedia.org/wiki/Newton's_rings

 

[sophiecentaur]

, even if the color of the light is monochromatic,

'particularly' is the word. The more monochromatic, the more definite the nulls. Obviously, the first rings Newton observed were coloured but the wave model and th sharp nulls etc. involve an assumption about a single wavelength. Even today, has anyone actually done a calculation involving a continuous range of wavelengths?