I disagree. When the switch is off, the circuit is open. There is no current through the light, the light is OFF, the full line voltage (presumably 115-120V) should appear across the switch terminals.Yes, you are reading voltage thru the light bulb.
I still have to disagree. Whether the switch is inline or in a switch loop is irrelevant... electrically the two are the same.Both of you are right.....depends on how the bulb is wired.
If power is ran to the bulb and the switch is a switch leg, then yes, you will see the full voltage across the switch with the switch off.
But if power is ran to the switch....assuming the hot is being switched....one side of the bulb is tied to neut....the other side to the switch....with the switch off....you will read some voltage...though I find 50Vac to be a bit high unless the bulb is a CFL. The only way you could get that high of a reading is with no bulb, a CFL or LED or a really low wattage (high resistance) bulb.
Electrically...yes....measurement wise...not......and you showed yours wired different than what I was describing.I still have to disagree. Whether the switch is inline or in a switch loop is irrelevant... electrically the two are the same.