ACR MLG SMOKE IN CABIN ON APCH EXPEDITED APCH AND LNDG AND ACFT EMERGENCY EVACUATION.

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THE FLT WAS NORMAL UNTIL APPROX 8 MILES OUT ON FINAL APCH TO RWY 23L AT CLE. AT THAT POINT THE AFT FLT ATTENDANTS POSITION; NOTIFIED THE COCKPIT OF SMOKE IN THE MAIN CABIN. FIRST OFFICER WAS FLYING THE ACFT AND I WAS WORKING THE RADIOS. I IMMEDIATELY CONTACTED THE TWR FOR FIRE COVERAGE UPON LNDG. AT APPROX THE 4 MILE POINT ON FINAL; I CONTACTED THE FORWARD FLT ATTENDANT; FOR ADDITIONAL INFORMATION. FA INDICATED THE SITUATION HAD WORSENED. INDEED FOR THE REST OF THE APCH AND LNDG BOTH MYSELF AND FIRST OFFICER COULD HEAR YELLING TO THE PASSENGERS TO STAY SEATED. THE LNDG WAS VERY SMOOTH AND BRAKING WAS AGGRESSIVE YET NOT HARSH. THIS RESULTED IN A MINIMUM GND ROLL AND A TURN OFF AT TAXIWAY 'M'. AS WE TURNED FROM TAXIWAY 'M' ONTO TAXIWAY 'L'; F/O OPENED THE COCKPIT DOOR TO INVESTIGATE. HIS IMMEDIATE COMMENT WAS THAT WE HAD SOME TYPE OF FIRE AND THAT THE SMOKE WAS HEAVY. FROM THE COCKPIT THERE WAS NO ODOR OF SMOKE UNTIL THE COCKPIT DOOR WAS OPENED. A RIGHT TURN FROM TAXIWAY 'L' ONTO THE INACTIVE RWY 18/36 WAS ACCOMPLISHED; ENGINES WERE SHUTDOWN AND AN EVAC WAS INITIATED IMMEDIATELY. A COMPLETE EVAC OF THE ACFT WAS EXECUTED IN LESS THAN 2 MINUTES WITH ALL SLIDES DEPLOYED. HOWEVER; WHILE THE LEFT REAR SLIDE DEPLOYED; IT DID SO IN SUCH A WAY AS TO BE UNUSABLE. AFTER EVERYONE HAD LEFT THE ACFT; FIRE CHIEF AND I LOCATED THE SOURCE OF THE SMOKE TO BE IN THE OVERHEAD COMPARTMENT. I ALSO TALKED TO TWO OTHER LADIES WHO MENTIONED THAT THEY HAD SEEN THE SIDEWALL OR OVERHEAD PSU LIGHTS FLASH SEVERAL TIMES SOON AFTER TAKEOFF FROM EWR. ONE LADY COMMENTED THAT SHE THOUGHT SOMEONE HAD TAKEN A FLASH PICTURE. THE CULPRIT WAS FOUND TO BE A FLOURESCENT LIGHT BALLAST.