A beam of light in glass (n=1.5) strikes the glass-air interface at an angle of
Practice Questions
Q1
A beam of light in glass (n=1.5) strikes the glass-air interface at an angle of 60°. What happens to the light?
It is refracted into the air.
It undergoes total internal reflection.
It is absorbed by the glass.
It is scattered.
Questions & Step-by-Step Solutions
A beam of light in glass (n=1.5) strikes the glass-air interface at an angle of 60°. What happens to the light?
Correct Answer: Total internal reflection occurs.
Step 1: Identify the medium the light is traveling through. In this case, the light is in glass, which has a refractive index (n) of 1.5.
Step 2: Determine the angle at which the light strikes the glass-air interface. The angle of incidence is given as 60°.
Step 3: Calculate the critical angle for the glass-air interface. The critical angle can be found using the formula: critical angle = arcsin(1/n), where n is the refractive index of the glass. For glass (n=1.5), the critical angle is approximately 41.8°.
Step 4: Compare the angle of incidence (60°) with the critical angle (41.8°). Since 60° is greater than 41.8°, this means the light cannot pass into the air.
Step 5: Conclude that total internal reflection occurs because the angle of incidence is greater than the critical angle.
Refraction and Total Internal Reflection – Understanding how light behaves at the interface between two media with different refractive indices, specifically when the angle of incidence exceeds the critical angle.
Critical Angle – The minimum angle of incidence at which total internal reflection occurs, dependent on the refractive indices of the two media.
