Video Transcript
In this video, we will be observing
how materials with similar refractive indices can be used to make one of the objects
seem invisible!
This eyedropper is made of
glass. The liquid in the bottle has a very
similar refractive index to that of the glass used in making the eyedropper. This means that both the glass and
the liquid distort light by bending light rays in a very similar way. This fact can result in a rather
surprising phenomenon.
When we lower the eyedropper into
the bottle full of liquid, we can still see it. This is because the eyedropper is
currently full of air. Air has a different refractive
index to that of the glass that forms the eyedropper, so it bends light slightly
differently. But let’s see what happens when we
fill the eyedropper with the liquid in the bottle.
Now, the bottom of the eyedropper
is filled with the liquid. Remember, this liquid has the same
refractive index as the glass that is used in making the eyedropper. Because of this, the light entering
the bottle from behind is bent in exactly the same way by the liquid in the bottle,
the glass making up the eyedropper, and the liquid in the eyedropper before it
leaves the bottle again and enters our eyes. Therefore, we cannot see a
difference between the liquid and the glass. It looks to us like the eyedropper
is made of the same material as the liquid, and it cannot be told apart from the
liquid.
