Answer
By rubbing on the rim, vibration is set up in the glass and hence in the air.
When the frequency of vibration matches one of the resonant frequencies of the air column, standing waves are set-up in this air column, producing the sounds we hear.
Work Step by Step
By rubbing on the rim, vibration is set up in the glass and hence in the air.
When the frequency of vibration matches one of the resonant frequencies of the air column, standing waves are set-up in this air column, producing the sounds we hear.
