Why is this statement FALSE
During night time, in a pond of water you can see the image of the moon. It is because of the rectilinear propagation of light.
Why is this statement FALSE
During night time, in a pond of water you can see the image of the moon. It is because of the rectilinear propagation of light.
Water isn't totally transparent (I don't think any substance is), some light gets reflected, some absorbed, and some transmitted. For you to see the bottom of the pond, light has to penetrate through all of the water, bounce off the bottom, penetrate all the way up and get back into your eyes. That requires a relatively shallow pond, clear water and good light, but it's not uncommon. For you to see your image, light merely has to reflect off the surface and back to your eyes, which is very common.
There are two wrinkles to seeing your reflection. One is literal wrinkles: if the water is at all disturbed, due to flowing water or wind, the image on the surface becomes too distorted to make out. The second is, if the image of the bottom is bright enough, it can overpower your reflection, making it impossible to make out.
That last point is important. Any time you look directly at a smooth, flat surface of glass or water, your image is being reflected, but it may be overpowered by the image from the other side. If you're looking at a deep pool of murky water, you're likely to only see your own image, because not much light can get through to the bottom. If you're looking at a shallow pool of very clear water (like a swimming pool), the bottom of the pool is likely to be so bright that you can't make out your reflection. But it's somewhere in between, you can see both at the same time.
Originally Answered: What is meant by the 'rectilinear propagation of light'?
This is the phenomena wherein the “propgation”, or movement of light, is described as “rectilinear”, or in a straight line.
Light does not bend. This is the reason why you are unable to see around a corner.
Light, however, can be manipulated to act as though it is bending.
- Refraction is the manipulation of light by placing an object in its path whose density is different to the surrounding medium. This will cause light to either slow down or speed up, and in doing so, it’s direction will be changed
- Reflection is the bouncing of light off an object. If you place a mirror at a corner, you will be able to “see” around the corner, as light from around the corner is bouncing off the mirror and travelling towards your eyes.
Water isn't totally transparent (I don't think any substance is), some light gets reflected, some absorbed, and some transmitted. For you to see the bottom of the pond, light has to penetrate through all of the water, bounce off the bottom, penetrate all the way up and get back into your eyes. That requires a relatively shallow pond, clear water and good light, but it's not uncommon. For you to see your image, light merely has to reflect off the surface and back to your eyes, which is very common.
There are two wrinkles to seeing your reflection. One is literal wrinkles: if the water is at all disturbed, due to flowing water or wind, the image on the surface becomes too distorted to make out. The second is, if the image of the bottom is bright enough, it can overpower your reflection, making it impossible to make out.
That last point is important. Any time you look directly at a smooth, flat surface of glass or water, your image is being reflected, but it may be overpowered by the image from the other side. If you're looking at a deep pool of murky water, you're likely to only see your own image, because not much light can get through to the bottom. If you're looking at a shallow pool of very clear water (like a swimming pool), the bottom of the pool is likely to be so bright that you can't make out your reflection. But it's somewhere in between, you can see both at the same time.
Originally Answered: What is meant by the 'rectilinear propagation of light'?
This is the phenomena wherein the “propgation”, or movement of light, is described as “rectilinear”, or in a straight line.
Light does not bend. This is the reason why you are unable to see around a corner.
Light, however, can be manipulated to act as though it is bending.
- Refraction is the manipulation of light by placing an object in its path whose density is different to the surrounding medium. This will cause light to either slow down or speed up, and in doing so, it’s direction will be changed
- Reflection is the bouncing of light off an object. If you place a mirror at a corner, you will be able to “see” around the corner, as light from around the corner is bouncing off the mirror and travelling towards your eyes.
