It is known that people with normal vision can read distant characters with a visual angle of not less than 5'( 1), and find the size of readable characters at a distance of 10m; (2) If you want to se

It is known that people with normal vision can read distant characters with a visual angle of not less than 5'( 1), and find the size of readable characters at a distance of 10m; (2) If you want to see clearly (1) Let the length and width of characters be lm, then l= 10α, where α=5'≈0.00 1454,

∴l≈ 10×0.00 1454=0.0 1454(m)≈ 1.45cm.

∴ The text size that can be read at a distance of 10m is about 1.45cm square.

(2) If people are at the distance of the slogan xm, then x=lα≈50.00 1454≈3439(m),

People with normal vision can see big slogans with a length and a width of 5m at about 3439 meters.