If the rays hit the bone then reflect off, would they not travel at a diagonal and not directly back at the machine to make such an image?
In: Physics
This is true for perfectly flat surfaces but realistically most things exhibit diffuse scattering where light is reflected all over the place.
Its like if you shine a flashlight at a wall, you can see the where the light hits the wall even if you shine it at an angle away from you
medical X-rays arent reflections.
The X-ray goes THROUGH the substance into the film, and the substance absorbs some of the X-ray as it does depending on its density.
That being said, angle in = angle out is for reflections off a smooth surface like a mirror, with any rough surface there are smaller angled surfaces at every angle that diffuse the light hitting it causing it to scatter in all directions. This is why you can see at all.
You misunderstood a little how X-Ray work. It doesn’t reflect from your bones. You have a device that emitting X-Rays in front of you. And the film or screen that forms an image is behind you. X-Rays penetrate your body, but part of them is absorbed. And different materials absorb X-rays differently. And that difference is exactly what you see on your X-Ray. Bones are more dense, so they are brighter. If there is some metal it will be completely white.
The x-rays that bounce off are not measured. Simplistically X-ray machines emit a certain amount of rays, and do not pass through bone or metal. Essentially for each part of the image they measure the *proportion* of x-rays that make it through (conventionally this is adjusted such that the areas with more transmission are darker and the areas with less are brighter). The reader is on the opposite side of the machine that emits the rays, with the subject between them.
Here’s the ELI5:
As an analogy, imagine you have a line of people and 100 people trying to run through them under a certain time limit. With just a single line of people you can imagine that most people would get through. But what happens if you add a second line? Fewer will make it through in time because there’s more in the way. If you have a super thick line or crowd even fewer people, perhaps none, will make it through.
Now if those people running are also in a line and have to take a straight path, and the line is uneven (maybe 1 person thick in some places, maybe 10 in others, and in-between elsewhere). You record each spot where a person got through and put a transparent piece of red plastic over that square of wall. Now repeat that many times–in the thin areas of the blocking line the multiple layers of plastic will make the wall really dark red, the medium thickness areas some people will get through sometimes, but not always, so you’ll get medium shades of red proportional to the thickness of the wall, and where there are lots of blockers the wall will remain white.
Based on the pattern of white and darkness of the red you can make statements about which areas were thicker and thinner–and this is essentially how X-rays work, too. Through accumulation of scientific evidence we know what proportion of rays should get through certain tissues normally and can make assessments about areas that do not fit their “normal” appearance.
The X-Ray image is not showing where the rays reflect. It shows where it doesn’t penetrate. It’s basically a shadow, but with the dark and light areas inverted.
The body part is placed between the x-ray emiter and the sensor, so the rays that go through the bodypart are detected and represented as dark areas, while the areas with less detection are brighter. It’s similar to a negative of a photo. Just like the old photo films were negatives and via the revelation process the image would be “inverted” per se.
So the bones, being denser than flesh and muscles, let fewer rays through and therefore are shown as brighter areas.
The image is very sharp, because the sensor is good enough to detect with such quality and because the difference in density of bone and the surrounding tissue is very high. There is basically no “transition zone” where 50% of the rays go through so it would appear as a gray fuzzy area. It’s basically all or nothing – I’m exagerating, I don’t know the percentages, but the idea is the same, the bone does not gradually become muscle, it has a very clear boundary as a solid dense structure inside soft tissue.
When the X-ray bounces off your bones, that light is lost forever. That makes a big ol’ black spot on the image. When the X-ray passes all the way through you, that light is captured. That makes a big ol’ white spot on the image. (There are some parts that make a gradient, like fat. Some of the light went through; some didn’t).
The technician provides the negative; white becomes black, black becomes white. This makes the bones “stand out” in the image. X-ray wavelength is tiny, so a lot of them go through you, and it’s easy to get a good resolution picture.
X rays usually pass through things and are detected on the other side of the object. The change in how much is absorbed by various parts creates the image. There is backscatter x-ray nowadays, but those are mostly used for security, like finding weapons concealed on airplane passengers at airports.
Can we use this incidence-reflection angle to discover the optimal angle to reduce splash back from urinals?
Why would they travel diagonally if the machine is right on top of you? The xrays come straight down and reflect off to the side instead of back to where they came from? If that was the case you wouldn’t even be able to take a regular photograph with your camera.
And that’s not even how xrays work anyways. Think of the xray as a lamp. You’re put in front of the machine and they shine an Xray light on you. Behind you is a piece of film, that catches the light, the xrays, and turns black. The image you’re left with is you “shadow” when shone with xrays, where some of them go through you but some of them never reach the film, giving you an image on the film of your insides. It’s like shining a light on a transparent bottle with an object inside, against a wall. On the wall you won’t really see a shadow from the bottle because it’s transparent, but you will see the shadow of the object. In this case the object is your bones, through which xrays don’t pass through, and the bottle is your skin and soft tissue, most of which the xrays do pass through.
Not a whole lot of reflection or refraction going on in an xray image. It’s just a shadow, with bones being better at absorbing xrays and flesh being quite transparent.
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