M.Sc Physics

Yes.
Yes, distance learning degree is valid as same a regular degree. Distance learning is made for those who belong to the working professional. Just think if you want to do an MBA program or any other program from regular university then for this you'll have to resign your current job for studies where if you will get enrolled in distance learning university then you will not have to drop the job as in distance learning student gets online facility of learning.
As you point out on the validity I want to tell you my friend distance learning has value and most of the big universities in India as well as in abroad are transforming their universities into distance learning university.
Distance learning is always the first options of working professionals. Distance learning University must have UGC and DEB approval, If the university doesn't have those approvals then the degree will not be valid, So first check the approval and reviews then apply for admission in distance learning.