I have seen a $24 lens which is advertised as attachable to an iPhone camera. How do lenses like these work? Here is the item I am mentioning
The correct name for these add-on devices is “supplemental lens”. We can fit supplemental lens to most any camera. For the phone camera or any camera, they work in exactly the same way as eyeglasses. We can overlay a magnifying glass over the camera lens and the combination allows the camera to take pictures super close-up. We can position a camera lens behind the eyep9oece of binoculars and we can take a picture and the results will be a highly magnified view. We can turn the binocular around and photograph backwards thru the instrument and get a wide-angle view. These supplemental lens attachments have been in common use in the camera world for about 100 years. Applying supplanted lenses to cellphones is not a remarkable incident.