If light travels at 3 · 108 m/s and its frequency is 6 · 1015 hz, then its wavelength is: a) 10 · 107 m b) 5 · 10-8 m c) 5 · 10-7 m d) 10 · 10-7 m

 5*10^-8 (B)

Explanation:  

-Given that the light is the speed

-We will be following the formula :

V= f (λ)

Where,  

V is the velocity  

F is the frequency  

λ is the wavelength  

3*10^8 = (6*10^15 )* λ

(3*10^8)/ (6*10^15 ) =  λ

5*10^-8m = λ answer

Note: λ is initially 0.5*10^-7 but to make it in the standard form it should be 5*10^-8. And do not forget to place the unit for the wavelength i.e. meter(m) otherwise you may lose marks!

it is very well related to a lot of things but with my limited knowledge i can confidently say that the answer is space.