Subject: If electromagnetic waves are massless, how can they transfer momentum?

I am a physics teacher and my AP kids are quite astute. We will be talking about the transfer of momentum and energy via electromagnetic waves this week and I am having difficulty with the concept of a massless electric and magnetic fields that are able to transfer momentum. Classically, momentum is thought of as "inertia in motion" and thus requires mass in order to exist. So how does light manage to transfer mometum - and then exert a radiation pressure?

Re: If electromagnetic waves are massless, how can they transfer momentum?