#8e MC15
#longitudinal wave
#9e MC17
#refractive index
#10e MC18
#stationary wave
#11e MC19
#electromagnetic wave
#12e MC22
#sound
#14e MC21
#lens
#13e MC23
#ultrasound
#longitudinal wave
#refractive index
#stationary wave
#electromagnetic wave
#sound
#lens
#ultrasound