8 min read•june 18, 2024
Saarah Hasan
Daniella Garcia-Loos
Saarah Hasan
Daniella Garcia-Loos
When light travels from one medium to another, some of it is transmitted, some is reflected, and some is absorbed.
**Reflection—**The light bounces off the surface; the reflection of light on a mirrored surface results in the formation of an image.
**Absorption—**The light is converted to another form of energy, usually heat (the light disappears as it enters another medium).
**Transmission—**The light goes right through one medium to another.
Okay, so that was a super brief explanation. Let’s get a bit more in-depth. 🧐
Like we mentioned before, light has the ability to seemingly bounce (or reflect) off of a surface. There are two kinds of reflections: specular and diffuse.
**Specular—**reflections off of a smooth surface; the orientation of the incoming light rays are preserved
**Diffuse—**reflections off of a rough/uneven surface; the incoming light rays are scattered in different directions.
When light hits a smooth, reflecting surface (), it reflects at the same angle on the other side of the line perpendicular to the surface.
In the image above, the light ray approaching the boundary of another medium is the incident ray, and the light ray leaving it is the . At the point where the light ray hits the boundary (the point of incidence), a line perpendicular to the surface can be drawn. This line is known as the , and it divides the angle between the incident ray and reflected ray into two equal angles. The ray that passes through into the new medium is known as the refracted (or transmitted) ray.
The angle between the incident ray and the normal line is the , the angle between the reflected ray and the normal line is the , and lastly**,** the angle between the and the normal line is the .
The states that the angle of incidence (θi) is equal to the angle of reflection(θr).
θi=θr
Let's expand on the refraction of light. (Here's an interactive.)
Just as we mentioned in 6.1, depends on the medium. When light rays change speed as they travel from one medium to another, the light appears to bend. Refraction is essentially this "bending". However, if there's no change in speed or if the angle of incidence is zero as the light passes from medium to medium, there'll be no refraction.
When light travels from one medium to another and slows down (the angle of refraction is less than the angle of incidence), the light is been refracted towards the normal. When light travels from one medium to another and speeds up (the angle of refraction is larger than the angle of incidence), the light is been refracted away from the normal.
One thing to keep in mind: when light refracts, its doesn't change.
When light travels through a material medium, it gets absorbed and re-emitted, which causes its apparent speed v, to be some fraction of c=3.00 * 10⁸ the speed of light traveling through empty space/vacuum). The reciprocal of this fraction, which essentially describe how fast light travels through the material, is the medium’s index of refraction:
n=c/v
Some things to remember about the index of refraction:
The equation that relates the angle of incidence and angle of refraction involves the index of refraction of the incident medium (n₁) and the index of refraction of the refracting medium (n₂) and is called Snell’s Law:
n₁sinθ₁=n₂sinθ₂
If n₂>n₁, θ₂<θ₁ - the ray will refract toward the normal
If n₂<n₁, θ₂>θ₁ - the ray will refract away from the normal Here are some key points about :
Snell's law is a fundamental principle in optics and is used to understand and analyze the behavior of light in different media and to predict the behavior of optical devices and systems. It is a useful tool for designing and troubleshooting optical systems and devices.
Snell's law is based on the principle that the ratio of the sines of the angles of incidence and refraction is equal to the ratio of the refractive indices of the media. This relationship is described by the equation n₁sinθ₁ = n₂sinθ₂, where n₁ and n₂ are the refractive indices of the media, and θ₁ and θ₂ are the angles of incidence and refraction, respectively.
Snell's law is a consequence of the wave nature of light and the fact that light can be reflected and refracted at boundaries between media. It is based on the observation that light is refracted at a certain angle when it is incident on a boundary between two media with different refractive indices.
Snell's law is used to predict the angle of refraction of light when it is incident on a boundary between two media with different refractive indices. It is also used to understand and analyze the behavior of light in different media and to predict the behavior of optical devices and systems.
As we mentioned previously, when light is refracted from a medium with a high index of refraction to one that has a lower index of refraction, it refracts away from the normal. As the angle of incidence increases, the angle of refraction becomes larger. When the angle of incidence reaches a critical angle, θc, at which the angle of refraction equals 90 degrees, the refracted beam is directed along the surface.
If the angle of incidence exceeds θc, there is no angle of refraction. The light will be reflected back into the original medium, a phenomenon called .
The critical angle can be found in the equation:
sinθc=n₂/n₁ (n₂<n₁)
If θ₁>θc, then total internal reflection will occur.
Total internal reflection is a phenomenon that occurs when light is incident on a boundary between two media with different refractive indices and is reflected back into the same medium. The critical angle is the angle of incidence at which total internal reflection occurs.
Here are some key points about total internal reflection and critical angles:
B) 30°
C) 45°
D) 90°
E) 180°
A) n₁ > n₂ > n₃
B) n₁ > n₃ > n₂
C) n₂ > n₃ > n₁
D) n₂ > n₁ > n₃
E) n₃ > n₁ > n₂
A) 1.4
B) 1.5
C) 2.1
D) 3.5
E) 5.0
B) wavelength
C) speed
D) angle
E) all will change
A) v₃ > v₁ > v₂
B) v₁ > v₂> v₃
C) v₁ > v₃ < v₂
D) v₂ > v₃ > v₁
E) v₂ > v₁ > v₃
A) a smooth surface B) a rough surface C) a boundary between high index of refraction and low index of refraction materials D) a boundary between low index of refraction and high index of refraction materials E) a boundary between any two transparent substances, regardless of index of refraction