answer: 340 m/s
explanation: in this instance, the sound wave travels 340 meters in 1 second, so the speed of the wave is 340 m/s. remember, when there is a reflection, the wave doubles its distance. in other words, the distance traveled by the sound wave in 1 second is equivalent to the 170 meters down to the canyon wall plus the 170 meters back from the canyon wall.
First you see the difference in mass numbers 238-234 = 4
Its is an alpha particle as it decreases the mass no by 4 .
Sometimes scientists make a mistake or Miscalculate and need to do the experiment again.