If you can see the face of a friend who is underwater, can she also see you?
Please explain. Thanks :)
yes, reciprocity, light paths work in both directions.
To answer your question, we need to consider a few factors. When light passes from one medium to another, such as from air to water, it undergoes a change in speed and direction. This phenomenon is called refraction.
When you look at your friend's face underwater, you are observing the light that reflects off her face and passes through the water. The light rays from her face travel through the water, and upon reaching the water-air interface, they undergo refraction again as they move from water to air.
Since the light rays change their direction upon exiting the water, it can cause an optical illusion. The refraction might make it appear as if your friend's face is in a different location than it actually is. This is because the light rays bend as they transition between the two mediums, distorting the image.
So while you can see your friend's face underwater, it does not necessarily mean that she can see you clearly from underwater. The distortion caused by refraction can make it challenging for her to see you accurately. However, if she is close enough to the water's surface, she might still be able to see some objects above the water, including you.
It's important to note that the extent of this distortion depends on several factors, such as the angle of observation, the depth of the water, and the clarity of the water. In some cases, the distortion might be minimal, allowing for clearer visibility between you and your friend.