Jefferson National Laboratory near Newport News VA has one o

Jefferson National Laboratory, near Newport News VA has one of the worlds most powerful light sources. If one of these sources were suddenly turned on, how long (how much time) would it take the beam to reach a target room 1.65 km away. Express your answer as a number (no powers of ten) with an appropriate prefix value. b) Imagine an experiment where a beam of light travels first a distance of 25.000 m through air, and then is reflected by a mirror for a return trip through glass (index of refraction 1.65) back to its starting point. What would be the time difference for these two parts of the round trip?

Solution

1. (a) t = d / c = (1.65 x 10^3 m) / (3 x 10^8 m/s)

= 5.5 x 10^-6 sec

(B) time taken to reach glass:

t1 = 25000 / (3 x 10^8) = 8.33 x 10^-5 sec

for return trip:

v = c/n

t2 = n 25000 / c = (1.65 x 25000 ) / (3 x 10^8) = 13.75 x 10^-5 s

t = t1 + t2 = 2.208 x 10^-4 sec