A mechanical device is something that takes energy input, modifies it, then outputs it in such a way that it assists in the performance of a task. A lens takes light input, modifies its vector, then outputs it in such a way that assists the performance of the eye.

 

So is a lens a mechanical device? I think so, but I'm having a hard time convincing a friend that glasses are mechanical devices. He keeps saying it must have moving parts to be a mechanical device.

Hmm, guess it depends what mechanical means. I usually think of mechanical as moving parts with no electricity involved. But a guess a machine could be any useful device.

I considered a machine to be something that takes in energy in one form and then outputs it in another form. say a car engine input:chemical energy(petrol) output:kinetic

But by the definition that you gave of a machine then a lens would be a mechanical device.

A mechanical device is something that takes energy input, modifies it, then outputs it in such a way that it assists in the performance of a task.

A transistor can do the same thing, now is that mechanics or electronics ?

 

I guess it all depends on personal definitions of the word mechanics and in which context it's used.

 

For me mechanical is more like moving parts in a machine.

I have to agree with your friend. Mechanical, to me, implies motion of parts. In classical physics you can break down studies into mechanics, electrodynamics, and optics. (and more advanced can get into solid state, and others). There's some overlap, to be sure, but these are general categories.

 

A lens is an optical device.

Maybe a good way to think of something mechanical is in terms of mechanical energy - namely, kinetic energy and the forms of potential energy that are considered "mechanical" - gravitational and elastic. So, if a device deals with these forms of energy (macroscopically, of course), it is a mechanical device.

 

So, in that context, I would not call a lens "mechanical".

Lol.

What a great question.

The machines that I know of are the lever and the inclined plane.

There may be a few more.

I really like your way of thinking about light…

and the way you have asked this question.

 

Perhaps the forces that make photons act as they do-

could be considered in terms of the inclined plane and the lever.

 

You may really be on to something big here.