My Question is as follows.

What is the effect of refractive index of an object for imaging (Photographs by high speed camera) on its size and shape information incurred from image?

Lets say ,

I keep the camera focal length, aperture, distance between camera & object, light intensity of the background constant. Put two objects of same diameter 'd' with different refractive index n1 and n2 in front of the camera one at a time. Size incurred from image of those object is of diameter d1 & d2.

My question is will d1 & d2 be the same ? or it will differ? if it differs how can I co-relate analytically/ theoretically or by ray tracing projection?

  • 2
    $\begingroup$ Can you draw a diagram, it's hard to understand your question. $\endgroup$ – boyfarrell Mar 7 '13 at 0:53

A while back I did an experiment imaging oil droplets in water, where we used oils of differing refractive index. Is this the sort of thing you're interested in?

If so, assuming your camera is in focus it will accurately record the size of the oil droplet so varying the refractive index will not cause the apparent size of the drop to change. However the difference between the refractive index of the oil and the refractive index of the water will affect the contrast.

To see this imagine using an oil with the same refractive index as water. Because there is no refractive index at the oil/water boundary there will be no reflection of light and therefore the oil drop will be invisible. As you increase the refractive index of the oil you increase the amount of light reflected at the edges of the drop and it becomes easier to see.

  • $\begingroup$ Thank you so much for your answer. I was thinking the same way. Do you happen to have or know any reference that I can use to show that refractive index doesn't makes a difference in the apparent size of the image? I will be working with rain drops which acts as a spherical lens itself. So, I was thinking would that be an issue. $\endgroup$ – Chowdhury Mar 10 '13 at 22:13
  • $\begingroup$ You are imaging the air-water interface not the water inside the raindrop, and the light from the interface isn't passing through the raindrop and therefore can't be affected by it. $\endgroup$ – John Rennie Mar 11 '13 at 6:54
  • $\begingroup$ Thank you again. Do you know any reference or journals or books that i can refer regarding this matter? $\endgroup$ – Chowdhury Mar 13 '13 at 15:07

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