  In the current analysis, we use spectroscopic observations of the quiet-Sun
made by IRIS instrument, and investigate wave propagation. We analyze various
spectral lines formed in different atmospheric layers such as the photosphere,
chromosphere, and transition region. We examine Doppler velocity time-series at
various locations in the quiet-Sun to determine the dominant oscillation
periods. Our results executing statistical analysis resemble those of the
classical physical scenario, indicating that the photosphere is mainly
characterized by the dominant 5-minute period, while the chromosphere is
primarily associated with the 3-minute oscillation period. In the transition
region, we observe a variety of oscillation periods, with dominant periods of
3, 8, and 12 minutes. We estimate the cut-off frequency by deducing phase
difference between two Doppler velocity time-series obtained from spectral line
pairs in different atmospheric layers formed at different temperatures. It
reveals a significant correlation between 3-minute periods in TR and
photospheric oscillations, suggesting that these oscillations in the TR might
propagate from the photosphere. Additionally, we analyze the phase difference
between chromospheric oscillations and photospheric oscillations, demonstrating
that only the 3-minute oscillations propagate upwards. Based on the statistical
analyses, we suggest the presence of magnetoacoustic waves in the solar
atmosphere in which some are propagating from the lower solar atmosphere
upward, while some others are propagating downward. TR carries both long-period
oscillations generated in situ, and some photospheric oscillations which are
also able to reach there from below.
