Does ray tracing render time depend linearly on image resolution?

(I'm not quite sure whether this question really belongs on this particular Stack Exchange, but I don't know where else to ask. If people think it's inappropriate for this SE, I'll be happy to move or delete it.)

I'm using a ray tracing program, POV-Ray, to render a 3d scene I've been working on. A low resolution test render already took a long time to complete (about 5 hours), and it'd be nice to have a preliminary estimate for the render time of the final high resolution image. So my question is: Does the amount of time it takes to render the scene depend linearly on the desired image resolution, all other things (such as field of view and aspect ratio) being equal? That is, if I increase the resolution from 1 MP to 10 MP, does the render time increase from 5 hours to 50 hours (or thereabouts)?

Any help would be greatly appreciated. Thanks for reading!