Question

Green laser light with a wavelength of 650 nm travels towards a photodetector.

a.How long does it take the laser to reach the photodetector located 50 meters away?

b.What is the change in the arrival time of the light if a 1 meter block of lucite is placed along the path for the laser to travel through? (index of refraction = 1.50)

c.What is the speed of light through the lucite?

Next, take a second laser (red) with wavelength of 720 nm and also place it 50 meters from the photodetector.

d.You machine a new block of lucite such that when the red light passes through the block, it arrives at the photodetector at the exact same time as the green light traveling through the 1 meter block in part b. Is the lucite block for the red light longeror shorter than the 1 meter lucite block used for the green laser light?

e.What is the speed of the red laser through the lucite? f.What is the lengthof the lucite for the red light?

Answer 1

(a) time = distance Speed = t = 50 3x108 -8 = t = t = 16.66 x i S = 166.66ns (b) t tul er 4am Speed in medium of lucite is - V = C ula = v= 3x10 2 x 100 m/s 1.5 t= titte = + time taken to traud 50m is, 49 3x108 - t = 16.83x108 5 = 8 2 x 10 = 168,3 ns. Change in arrival time, at= t-t = 4t = 1.7ns s 1.66 ns = (c) Speed through lucite is ra 2 8 =) = 3x10 2x108 m/s 1.5 (d) Speed for both lights are luchte Because le C -) V- gro รา Same in the medium n= constant Hence v = constant for both lights

Hence of same length im as that forgreen. it is length im (e) speed of red laser light is = ļ 3x108 - 2x10m รา lis (f) The lengl5 of licite for for the red light is im