The "Type" attribute of Image in "Sitecore Select Media" popup is showing as "Image" instead of "Jpeg"

When I click on Browse link of any image field in my sitecore 8.1 instance, the type of Image is displaying as "Image" instead of "Jpeg". I guess some setting went wrong. Please point out me in right direction.

My Bad. It is occuring only for png images. It is fine absolutely for Jpeg images.Thanks for ur support.