What energy transformation takes place using a DVD player?

Answer 1

Electrical energy changes to light and sound energy.

Answer 2

The electromagnetic (EM) waves in a DVD player appear as light in the laser. The electrical energy the machine uses drives (among other things) a laser. The laser beam hits the reflective material on the DVD, and the reflected beam is modulated by that spinning, reflecting surface of the disc. The signal is seen and then demodulated into the audio and video. The transfer of energy could be seen as the transmission of EM energy (light) by the laser to the surface of the disc and its reflection from there to the photodiode that looks at the amount of reflected light.