Refraction of Light & Image Quiz

What is the velocity of light in water vwater?

How long does it take for light to travel 250 m in water? (n = 1.33 for water).

What are the two basic laws of refraction?

What is chromatic dispersion?

According to Fermat’s Principle, what does light take?

What happens when light enters a denser medium?

What is total internal reflection?

hen light is incident from a high dense medium (refractive index n1) to a low dense medium (refractive index n2) (n1 > n2) Consider the light source “S” is in the medium “1” and five rays A, B, C, D, and E are going in different directions: Ray “A” passes into medium 2 normal to the interface: (Incidence angle = refracted angle = 0) Ray “B” with incident angle “θ1” refracted away from the normal at an angle “θ2” (As n1 > n2, so θ2 > θ1). As the incidence angle “θ1” increases the refracted angle “θ2” also increases until at the critical angle “θc” the refracted ray “D” emerges tangent to the surface. The critical angle “θc” is the limiting angle of incidence in a denser medium which results in an angle of refraction of 90o. Ray “E” with an angle greater than “θc” is reflected back inside the medium “1” (total internal reflection), and Incidence angle = reflection angle.

Critical angle “θc” can be calculated by using Snell’s law: Since “sin θc” can never be greater than “1”, “n1” must be greater than “n2”. As the critical angle for glass is 42o (arcsin (1/1.52) = 42o), so in many optical instruments, 45o prisms are used. In both cases, total internal reflection occurs because the angles of incidence are all 45o (greater than the critical angle).

The diamonds are known for their impressive shining quality. Their shining quality is mainly due to the total internal reflection of light inside them. The critical angle for the diamond-air interface is very small (About 24.4o). Once light enters a diamond total internal reflection takes place inside the diamond. The impressive shining quality of the diamond is not by nature but because of the technical skill of a diamond cutter.