Specify image size in desktop and mobile

Hi,

When I create a slidable object as slider to be used on a page, the images on the desktop appear fine with the proportions I would like, in this case 16:5 (images cut to this size in advance).
How can I specify another proportion for the images when showing on mobile without stretching them. What im looking to achieve is, set the image proportion to 16:11 and cut the remaining pieces on the sides. This way I can have a bigger image on mobile.

Thanks!