Optical Communication Systems

To obtain a power of 1μW of light at a wavelength of 0.85 μm, how many photons are needed per second?

• 4.29 x 10^12
• 8.67 x 10^11
• 2.15 x 10^12
• 1.00 x 10^13

What happens when light strikes a point of change in the refractive index and scatters in all directions?

• Light reflects off the surface without scattering.
• Light travels in a straight line without any change.
• Light scatters in all directions due to changes in the refractive index.
• Light is absorbed completely without scattering.

If light leaves a material with a refractive index of 1.45 and penetrates the boundary into another material with a refractive index of 1, what will be the Fresnel loss?

• 2.10%
• 5.00%
• 3.65%
• 1.25%

Calculate the angle labeled θ2 in the image below. The first material has a refractive index (n1) of 1.51 and the angle of incidence (θ1) is 38˚, while the second material has a refractive index (n2) of 1.46.

• θ2 ≈ 41.2°
• θ2 ≈ 39.8°
• θ2 ≈ 45.0°
• θ2 ≈ 35.5°

The event of light reflection occurs when the angle of incidence is such that the angle of refraction is exactly 90˚, causing the light to travel parallel to the boundary within the second material. From Snell's Law, n1 sin θ1 = n2 sin θ2, what is the critical angle?

• θc = arcsin(n2/n1)
• θc = n1 + n2
• θc = sin(n1/n2)
• θc = n1/n2

A beam of light travels in a transparent material with a refractive index of 1.51 and approaches the boundary towards a second material with a refractive index of 1.46. Calculate the critical angle for the light to travel parallel to the boundary in the second material.

• 30 degrees
• 75 degrees
• 45 degrees
• 60 degrees