gamma rays γ-rays

variable focus lens vari-focus lens

vari-focus lens variable focus lens

Roentgen rays {= X-rays}

X-rays (Roentgen rays)

β-rays (beta rays)

2 Focus

2D digital focus

2nd-order weak focus

a long focus mirror

Actinic Focus

activity focus

adjustment of focus

aerodynamic focus

alternate solenoid field focus

annular focus

anterior focus

apparent focus

arbitrary order weak focus