Physics 2016 JAMB Past Questions - Question 11: A Glass plate 0.9cm thick has a refractive index of 1.50. How long does it take for a pulse of light to pass through the plate ?

Correct Answer

B

Explanation

The speed of light in a medium is given by the equation:

v = c / n

where v is the speed of light in the medium, c is the speed of light in a vacuum (approximately 3 x 10^8 meters per second), and n is the refractive index of the medium.

In this case, the refractive index of the glass plate is 1.50. Therefore, the speed of light in the glass plate is:

v = (3 x 10^8 m/s) / 1.50 = 2 x 10^8 m/s

Now, we can calculate the time it takes for the pulse of light to pass through the plate. The time is given by the equation:

t = d / v

where t is the time, d is the thickness of the plate, and v is the speed of light in the plate.

In this case, the thickness of the glass plate is 0.9 cm, which is equal to 0.009 meters. Therefore, the time it takes for the pulse of light to pass through the plate is:

t = (0.009 m) / (2 x 10^8 m/s) = 4.5 x 10^-11 seconds

So, it takes approximately 4.5 x 10^-11 seconds for a pulse of light to pass through the glass plate.