I believe the correct answer is 40 cm.
If you mean electromagnetic waves
Radio waves can be used well in radio signals
Infrared in remote controls
X rays for x-rays
Gamma rays in a nuclear power plant
Uv rays can cause cancer but they transmit vitamin D
A human has 46 chromosome pairs. For a baby to be a boy its needs to have a xy chromosome and for it to be a girl it has to be xx.