What evidence indicates that the Earth is 4.6 billion years old? using carbon 14 dating methods on earliest life forms
using the radiometric dating of early Earth rocks
calculating the cooling rate of the Earth's mantle
adding up the layers of rock strata​

In uranium-lead dating, for instance, the radioactive decay of uranium into lead proceeds at a reliable rate. Based on the very old zircon rock from Australia we know that the Earth is at least 4.374 billion years old.

And that's how after rounding we know that earth is 4.5 years old.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave