If you are going to have invisibility (or cloaking devices) in your book you may want to consider the following:
First you have to decide if light goes straight through an object or around it.
If light goes through an object then it’s a bit like glass, where there might be some refraction, if this occurs will make an object near invisible and still detectable.
The main problems occur however when the invisible object is a person. That person will effectively be blind. Why? Because the person’s retinas are invisible, the light will go straight through and will not be converted to electrical impulses to be sent to the brain. OK, don’t make the retinas invisible, (this is what HG Wells did in the invisible Man) but then you hit other problems, in that light will be hitting the retinas from all angles and will not have been focused by the lens, (unless it’s not invisible). So again the invisible person will be blinded, this time by bright light.
The other alternative is to have light go round an object. This also leads to problems because if all the light goes round an object then anyone inside will not be able to see as well as all light is avoiding them.
You could allow cameras to transmit information to those inside, but then these would be visible.
If you have light going round an object (which has been done on small objects with certain frequencies) then you have to ensure that all light continues on its journey as if nothing had happened, because the slightest imperfection could be detectable.
A technological solution is to have cameras on one side of the object capturing the light and projectors on the other side retransmitting the light. A film that did this well was Predator (the predator was near invisible). One that did it badly was the James Bond film with the invisible car in Iceland.
The main problem is that no matter how good the technology the retransmitted light will have a source closer than the original light and would be detectable by our stereoscopic vision. This technique could make objects difficult to see but will not provide true invisibility.
Of course you can ignore all of the above by using magic, have very sophisticated technology that overcomes all of the above problems or just hope that the reader doesn’t think about it too much.
This article is supposed to get you thinking not stop you having invisibility in your book.
Tom Greenwood is a married father of two living in Edinburgh. He has a Zoology degree and had what he thought was a good idea for a book which he has written in his spare time. He has not done all that much interesting in his life, perhaps now he has written a book that will change.