Some pupil thinks that we can see objects which are not light sources because our eyes give out light, just like a torch. How can you show that the idea is wrong?
Answers
Answer:
We do not see light itself. I have explained it at length in my upcoming book “Descriptive Knowledge, Mind and Reality - A case of Epistemological Realism”.
Following I am copying relevant portion from this book:
1.6.5 How Mind Sees External Objects
Reality is also mathematics but not like this model assumption based mathematics. Model is a supposed closed system whereas reality is a real open system. Reality may not be foreseeable to mind but it is seeable to mind. We can see real objects only when they are within light field or waves created by a light source however some animals like bats may be able to ‘see’ objects through sound waves. Light field is usually created by a glowing or luminous object and the presence of such a field induces a dull glow to the real objects that exist within the field. We do not see light field, we only see glowing objects that include source glowing object as well as all those objects who have acquired dull glow due to the presence of light field surrounding them. The apparently lighten up empty area before source glowing object or around visible dull objects is not the light field itself but consists of glowing concentration of molecules of atmosphere. To create a light field, all we need is a source glowing object may it be wild fire, a candle light, a light bulb or Sun. The field created in this way is usually a spherical outwardly spreading field such that outward flow is blocked by the presence of physical objects in the way. The resultant effect is that the light facing side of object acquires dull glow and becomes visible such that back side of object, though in theory should be devoid of light field but somehow acquires a darker shadowy glow. The reason for such a darker shadowy glow may be continuous interaction of those glowing molecules of atmosphere which are outside shadowy area with those of inside area who will acquire a down step secondary dull glow in this way.
no they are right!
We see objects because they either give off their own light, or light reflects off the objects and enters our eyes. The moon is an interesting example. It doesn't make its own light – we can see the moon because it reflects light from the sun. If an object did not reflect any light, we would not be able to see it.