If the waveform of a pure sine wave when viewed on an oscill

If the waveform of a pure sine wave when viewed on an oscilloscope is such that it appears that the earlier cycles have a longer period then the later cycles (as viewed on the CRT), what would be the reason for this

Solution

As the it is having less frequency input than the intial frequency input the earlier cycles have longer preiod than the later cycles. This is works accoding to the faradays law.