Intensity of laser when hitting a diffuse surface

I am receiving a 5W laser from China which is 1000x more powerful to that cheap 5mW I have (I know it'll be closer to 1W but... for sake of argument)

I think that 5W shouldn't be pointed at a white wall (diffuse surface) without wearing goggles.

A friend tells me it's not a problem because of how light diffusion works.

What's the physics of laser hitting diffuse surface? How much power bounces back at 10m?

In terms of mW/square mm, not much @ 10m. But the dot can be very uncomfortable to look at.

Thanks Wizard.

How does the mW/m2 drops with view distance?

Also I notice when I shine the puny 5mW to the wall, the dot of light seems to retain some of its coherence (what I'd call that laser vibe) as opposed to turn into a normal diffuse light why is that? Does that have an impact is the amount of power reaching the retina.