You are standing at x90km and your assistant is standing at

You are standing at x=9.0km and your assistant is standing at x=4.0km. Lightning bolt 1 strikes at x=0km and lightning bolt 2 strikes at x=15.0km. You see the flash from bolt 2 at t=14s and the flash from bolt 1 at t=60s.

If not, what was the time difference between the two?

Solution

The Clocl starts at t=0

1.At t=14 us ,you see the flash from bolt 2

2.At t=60 us ,you see the flash from bolt 1

Light from both the bolts travel at the speed of light

3*10⁸ m/s =300 m/us

TIme taken by Bolt 1 reach you

T₁ = 9000/300 =30 us

Since you see bolt 1 at 60 us ,so it strikes after 60-30 =30 us.

TIme taken by Bolt 2 reach you

T₂ =4000/300 =13.33 us

Since you see bolt 2 at 14 us ,so it strikes after 14-13.33 =0.67 us

Therefore strikes are not simultaneous ,So time difference between the two is

T=30-0.67 =29.33 us