What are the main properties of X-rays and γ-rays?

X-rays and γ-rays have the following properties in common:

1. invisibility; they cannot be perceived by the senses

2. they travel in straight lines and at the speed of light

3. they cannot be deflected by means of a lens or prism, although their path can be bent
(diffracted) by a crystalline grid

4. they can pass through matter and are partly absorbed in transmission.

5. they are ionising, that is, they liberate electrons in matter

6. they can impair or destroy living cells

What is influencing the penetrating power of X-radiation?