Incident Angle of 90 Degrees on a Glass Slab

When a ray of light enters from air and is incident on the surface of a glass slab at an angle of 90 degrees, the measure of the angle of refraction can be determined by applying the laws of refraction.

Law of Refraction
The law of refraction, also known as Snell's law, describes the behavior of light as it passes through different mediums. It states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the velocities of light in the two mediums.

Angle of Incidence
The angle of incidence is the angle between the incident ray and the normal to the surface of the medium at the point of incidence. In this case, the angle of incidence is 90 degrees, which means the incident ray is perpendicular to the surface of the glass slab.

Angle of Refraction
The angle of refraction is the angle between the refracted ray and the normal to the surface of the medium at the point of refraction. To determine the angle of refraction, we need to consider the refractive indices of the two mediums involved.

Refractive Indices
The refractive index of a medium is a measure of how much the speed of light is reduced when it passes through that medium compared to its speed in a vacuum. The refractive index of air is approximately 1, while the refractive index of glass is typically around 1.5.

Calculation
Using Snell's law, we can calculate the angle of refraction. The formula for Snell's law is:

n1 * sin(angle of incidence) = n2 * sin(angle of refraction)

Since the angle of incidence is 90 degrees, the sine of 90 degrees is 1. Therefore, the equation becomes:

n1 = n2 * sin(angle of refraction)

Substituting the refractive indices, we have:

1 = 1.5 * sin(angle of refraction)

Simplifying the equation, we find:

sin(angle of refraction) = 1/1.5

Taking the inverse sine of both sides, we get:

angle of refraction = arcsin(1/1.5)

Using a calculator, we find that the angle of refraction is approximately 41.8 degrees.

Conclusion
When a ray of light entering from air is incident on the surface of a glass slab at an angle of 90 degrees, the angle of refraction is approximately 41.8 degrees. This can be calculated using Snell's law and considering the refractive indices of air and glass.

90 degree