Question

By what percent is the speed of blue light (450 nm, n450nm = 1.465) less than the speed of red light (680 nm, n680nm = 1.450), in fused quartz (Figure 1)?

Answer 1

Here,

speed of blue light , vblue = c/refractive index

vblue = c/1.465

speed of red light , vred= c/refractive index of red light

vred= c/1.450

Now ,for the percent speed of blue light is slower than red light

percent = (vred - vblue) *100/vred

percent = (c/1.450 - c/1.465) * 100/(c/1.450)

percent = (1/1.450 - 1/1.465) * 100/(1/1.450)

percent = 1.02 %

the blue light is 1.02 % slower than the red light