Because of the ligting of the machine and you can go blind if theres no eye protection
Number two because that’s the answer
Use Pythagorean Theorem
C2 = a2 + b2
c2 = 20^2 + 48^2
c2 = 400 + 2304
c2 = 2704
c = 52
Let I represent intensity and and d the distance;
I

When I=8000
8000=

k=32000
I=

I=

I=265 units