## shortcake1970 how long does it take light to reach us from the sun, 1.49 X 10 to the 8th km away one year ago one year ago

1. shortcake1970

a red light has a wavelenght of 620nm. what is the frequency?

you can use v=s/t for the first and $$v=f \lambda$$ for the second.

note: light has a speed of $$3 \times 10^8m/s$$

4. UnkleRhaukus

$v=\frac dt\quad \implies\quad t=\frac dv$ $d=1.49\times10^8 [\text {km}]=1.49\times10^{11}[\text m]$$v=c=3\times10^8 [\text{m/s}]$

5. shortcake1970

Thank you!