Understanding the Concept of Ray of Light and Diffraction at Small Apertures

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In summary, diffraction occurs when light bends around an obstacle, with the size of the obstacle needing to be larger than the wavelength of light. This means that as the wavelength tends to zero, there will be no diffraction, even for extremely small apertures. The concept of "rays" is an artificial one and there will always be some level of diffraction present. The amount of acceptable diffraction can be determined by the width of the aperture and the wavelength, with the ratio of the two being a key factor. This is important to consider when discussing resolution and the diffraction limit.
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I can't get the concept why there is no diffraction when lambda tends to 0 even for extremely small aperture.please explain simply.
 

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Diffraction is light bending around an obstacle. Roughly, the wavelength of light must be larger than the size of the obstacle for light to bend around the obstacle. So if the wavelength of light is just "infinitesimally" bigger than zero, it will not bend around any obstacle with a finite size.
 
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Yogesh_2010 said:
I can't get the concept why there is no diffraction when lambda tends to 0 even for extremely small aperture.please explain simply.
A "ray" is a totally artificial concept which often works well when doing calculations to predict what waves will behave like.
To be strictly accurate - there is always some diffraction. Once you have decided how much diffraction is acceptable (e.g. how much energy appears in the sidelobes of a parabolic microwave reflector antenna or what resolution your optical telescope needs) you can determine the width of aperture you will need for a given wavelength.
The passage in that book is trying to put it in perspective. In the end, you are considering the ratio of wavelength to aperture. As the aperture gets less then so must the wavelength.
P.S. You presumably have read outside that particular passage in the book - concerning resolution and 'diffraction limit'.
 
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1. What is a ray of light?

A ray of light is a narrow beam of light that travels in a straight line. It is a simplified model used to understand the behavior of light. In reality, light travels as a transverse wave, but the ray model is a useful tool for understanding and predicting the behavior of light.

2. How does light diffract at small apertures?

Diffraction is the bending of light waves as they pass through small openings or obstacles. When light passes through a small aperture, it spreads out and creates a diffraction pattern. The size of the aperture and the wavelength of light determine the degree of diffraction.

3. What is the relationship between aperture size and diffraction?

The smaller the aperture, the greater the degree of diffraction. This is because smaller apertures cause more bending of the light waves, resulting in a more pronounced diffraction pattern. Larger apertures, on the other hand, produce less diffraction.

4. How does diffraction affect the image formed by a lens?

Diffraction can cause blurring or distortion of the image formed by a lens. This is because the diffraction pattern created by the aperture interferes with the incoming light waves, causing them to scatter and create a less defined image. This is especially noticeable when using small apertures or when photographing distant objects.

5. How do we use the concept of diffraction in everyday life?

Diffraction is used in many everyday applications, such as in cameras, telescopes, and microscopes. It is also used in fiber optics, which rely on the bending of light waves to transmit information. Diffraction gratings, which are made up of closely spaced slits, are used to separate light into its component wavelengths, making them useful in spectroscopy and other scientific experiments.

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