Question

what is the distance in km of a star from the earth from which light takes 20 years to reach us?

Answer 1

Hey buddy....
As u know speed of light is 3*10^8m/s
so for 1 min distance covered by light is 6*10^9m/m
and for an hour...36*10^10m/hr
and for a day 864*10^10 m/day
so for a month 2592*10^11 meter/month
and for a year 31104*10^11 meter/ year
so according to ur question u r asking that light took 20 years to cover that particular distance so need to multiply is by 20 nd i.e., 20*31104*10^11=62208*10^12 m
that is the distance in meters if u want in kilometers then just simply convert it...
Hope it will help u.. :)