ELI5: How come when you look at your reflection through the back of a spoon, your reflection is the right way up, but when you flip it the other way, it’s upside down?
Answer: When you look into the inward curve of the spoon, the light from your chin hits the bottom, bounces up to the top of the curve and then out towards your face.
Light from the top of your head does this opposite.
Since the top light ends up at the bottom, and the bottom light ends up at the top, the image you see is upside down.
When the light rays hit the surface, they bounce off at an angle, instead of directly back like a mirror.. When they do that along every point in the reflection, it flips the image.
Convex surface (the back of the spoon) tilt more”up” the further “up” you go, and more “down” the further down you go on the surface. So, two spots a little bit apart will bounce light back and spread out a little without the paths crossing.
Concave surfaces (like the front of the spoon) have an angle that tilts more “up” the further down you go, and vice versa. For a slightly curved surface, this just compresses the image in a little bit. But if it’s curved enough, the angle from the surface sends light back even more, and the paths cross, making images appear upside down.
Other people are answering the question you ask in the title, but I want to answer the other question. No, you’re not dumb. Questions like this are what people ask who enjoy understanding the world. Not knowing how the world works doesn’t make you dumb. Noticing that you don’t know how the world works and asking is the first step to understanding the world.
A concave mirror has a focal point. If you’re right against the mirror, the image will look almost normal. As you move further away from it, the image will look smaller and smaller, until it reaches the focal point, at which point it is (almost) a single dot. Once you move past that point, the image starts getting larger, but flipped. ><
A convex mirror does not have a focal point, so the image just gets larger and larger.
The proper explanation is long but requiers only basic geometry and ideal optics rules.
To make it simple as a starting point for this fascinating quest, let us consider that a concave mirror focused the light to a spot while the convex mirror does not.
This point of inversion is in front of the concave mirror ( for the convex mirror it is on the other side and requiers optical tricks to get ) but a simple analogy would be a convex lens and a concave lens.
I encourage you to find those and try to focus light with them, and observe how that goes !
Optics are a fantastic subject and many extradinary discoveries are still happening in it !
It’s the same reason why our eyes and cameras in general work. The concave surface is focusing the light into a small point, and after that it’s flipped, so if you had a shallow enough spoon it wouldn’t do it, or as you’re more likely to have experienced, with something like a ladle, the distortion from it also creates some very weird effects on how the reflection looks depending on how far away it is.
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Answer: When you look into the inward curve of the spoon, the light from your chin hits the bottom, bounces up to the top of the curve and then out towards your face.
Light from the top of your head does this opposite.
Since the top light ends up at the bottom, and the bottom light ends up at the top, the image you see is upside down.
Concave and convex mirrors and light refraction
When the light rays hit the surface, they bounce off at an angle, instead of directly back like a mirror.. When they do that along every point in the reflection, it flips the image.
https://buphy.bu.edu/~duffy/PY106/22c.GIF
Convex surface (the back of the spoon) tilt more”up” the further “up” you go, and more “down” the further down you go on the surface. So, two spots a little bit apart will bounce light back and spread out a little without the paths crossing.
Concave surfaces (like the front of the spoon) have an angle that tilts more “up” the further down you go, and vice versa. For a slightly curved surface, this just compresses the image in a little bit. But if it’s curved enough, the angle from the surface sends light back even more, and the paths cross, making images appear upside down.
Other people are answering the question you ask in the title, but I want to answer the other question. No, you’re not dumb. Questions like this are what people ask who enjoy understanding the world. Not knowing how the world works doesn’t make you dumb. Noticing that you don’t know how the world works and asking is the first step to understanding the world.
The image is then flipped again inside your eyeball. Your brain flips it a final time.
A concave mirror has a focal point. If you’re right against the mirror, the image will look almost normal. As you move further away from it, the image will look smaller and smaller, until it reaches the focal point, at which point it is (almost) a single dot. Once you move past that point, the image starts getting larger, but flipped. ><
A convex mirror does not have a focal point, so the image just gets larger and larger.
The proper explanation is long but requiers only basic geometry and ideal optics rules.
To make it simple as a starting point for this fascinating quest, let us consider that a concave mirror focused the light to a spot while the convex mirror does not.
This point of inversion is in front of the concave mirror ( for the convex mirror it is on the other side and requiers optical tricks to get ) but a simple analogy would be a convex lens and a concave lens.
I encourage you to find those and try to focus light with them, and observe how that goes !
Optics are a fantastic subject and many extradinary discoveries are still happening in it !
It’s the same reason why our eyes and cameras in general work. The concave surface is focusing the light into a small point, and after that it’s flipped, so if you had a shallow enough spoon it wouldn’t do it, or as you’re more likely to have experienced, with something like a ladle, the distortion from it also creates some very weird effects on how the reflection looks depending on how far away it is.