Why every textbooks put the light source in the horizontal line?

[Twukwuw]

in the diffraction experiment, the light source and the slit are in the same horizonatal line.

My question is, if the light source is placed at another position which is no longer in the previous horizontal line, would we still get the same diffraction pattern?
Will the diffraction pattern shift?

Thanks,
Twukwuw.

 

[quantumdude]

in the diffraction experiment, the light source and the slit are in the same horizonatal line.

Well if you rotate your book 90 degrees then they'll be in the same vertical line instead.

My question is, if the light source is placed at another position which is no longer in the previous horizontal line, would we still get the same diffraction pattern?
Will the diffraction pattern shift?

No, you won't get the same pattern. If the beam comes in obliquely then the wavefronts in the beam all travel different distances by the time they hit the screen. The path length differences will result in phase differences.

Sending the beam in perpendicular to the screen ensures that all wavefronts travel the same distance to the screen, and hence are in phase. You have to have that in order to get the nice clean diffraction pattern that is described so well by the equations in your textbook.

 

[charng]

I can provide an explanation for why textbooks typically place the light source in the horizontal line for diffraction experiments. This is because the horizontal line is the most common and convenient position for the light source and slit to be placed in relation to each other. Placing them on the same horizontal line allows for a more controlled and consistent experiment, as any changes in the distance or angle between the light source and slit can affect the diffraction pattern.

To answer your question, if the light source is placed at a different position, the diffraction pattern will most likely shift. This is because the distance and angle between the light source and slit will change, altering the interference patterns that are produced. However, the exact shift and pattern will depend on the specific positioning of the light source and slit, as well as the wavelength of the light being used.

In summary, the placement of the light source in the horizontal line for diffraction experiments is for practical and consistent purposes. Any changes in this positioning can result in a shift in the diffraction pattern. Further experimentation and analysis would be needed to determine the exact effects of different light source positions on the diffraction pattern.