▁not ▁know ▁about ▁the ▁threshold ▁of ▁stro bing . ▁ ▁Most ▁stro be ▁lights ▁on ▁sale ▁to ▁the ▁public ▁are ▁factory - limited ▁to ▁about ▁ 1 0 – 1 2   Hz ▁( 1 0 – 1 2 ▁flash es ▁per ▁second ) ▁in ▁their ▁internal ▁oscill ators , ▁although ▁extern ally ▁triggered ▁stro be ▁lights ▁will ▁often ▁flash ▁as ▁frequently ▁as ▁possible . ▁Studies ▁have ▁shown ▁that ▁the ▁majority ▁of ▁people ▁that ▁are ▁sus cept ible ▁to ▁the ▁stro bing ▁effects ▁can ▁have ▁sympt oms , ▁al beit ▁rarely , ▁at ▁ 1 5   Hz - 7 0   Hz . ▁Other ▁studies ▁have ▁shown ▁ep ile ptic ▁sympt oms ▁at ▁the ▁ 1 5   Hz ▁rate ▁with ▁over ▁ 9 0 ▁seconds ▁of ▁continuous ▁st aring ▁at ▁a ▁stro be ▁light . ▁There ▁have ▁been ▁no ▁known ▁se iz ures ▁at ▁or ▁below ▁the ▁ 8   Hz ▁( or ▁ 8 ▁flash es ▁per ▁second ) ▁level . ▁Many ▁fire ▁al ar ms ▁in ▁schools , ▁hosp it als , ▁stad iums , ▁etc . ▁stro be ▁at ▁a ▁ 1   Hz ▁rate . ▁ ▁See ▁also ▁▁ ▁Elect rot ach ys cope ▁ ▁T ach ometer ▁ ▁Zo etro pe ▁Jer k iness , ▁dis continu ity ▁in ▁motion ▁pictures , ▁also ▁called ▁stro bing ▁Phot ographic ▁flash , ▁often ▁referred ▁to ▁as ▁a ▁stro be ▁light ▁W agon - w heel ▁effect ▁Air - g ap ▁flash ▁ ▁References ▁▁ ▁Category : G as