Question

The speed of light in air 3 x 108 m/s. If the refractive index of glass is 1.5, find the time taken by light to travel a distance of 10 cm in glass.

Answer 1

Let us first find the speed of light in glass, thus
n = c/v
v = c/n
|Substituting|
v = 3*10^8/1.5
v = 2*10^8 m/s -----> [1]

Now, we know the formulae for finding 'TIME'
Time = Distance/Speed

Here, we need to convert Meter into Centimetre
Be careful while doing it!!

|Substituting|
T = 10cm/2*10^8 m/s x 0.01 (1cm = 0.01 m)
=10cm/0.02*10^8 m/s
=1/0.05*10^8 cm/s
=0.05*10^-8 cm/s (Exponent becomes negative when brought into the numerator
= 5*10^-10 seconds

Answer 2

Answer:

the answer is 2×10^8ms-1

Explanation:

tq