Ray (optics)

Light moves in lines.

We call these lines rays. A ray shows where light goes.

Rays can do many things. A ray can hit a surface and bounce. This is called reflection.

It is like a ball bouncing off a wall.

A ray can also go through a surface. This is called refraction. It happens when light moves from one thing to another. This can make the ray bend.

Light rays can also stay inside a thin wire. This is how some light moves through long paths. It stays trapped inside.

Scientists use these rays to study light. It helps them learn how things work.

Scientists use a model to study how light moves. They call these lines light rays.

A ray shows the direction that light power flows. In most places, rays travel in straight lines. But rays can bend when they move between different things. This bending is called refraction.

Rays can also bounce off a surface. This is called reflection. The Law of Reflection says the bounce angle matches the hit angle. When a ray hits a surface, it can also go through it. This is called a transmitted ray. The amount of power in the ray stays the same. It is either reflected, transmitted, or absorbed by the surface.

Computers use a way called ray tracing to study light. This method follows many rays through a system. It helps us see how complex lenses work. In thin wires called optical fibers, rays can stay trapped. These are called guided rays. They stay inside the core of the fiber.

Light is made of waves that move through space. Scientists use a special model to study how this light moves. They call these lines light rays.

A ray is a line that shows the direction of energy flow. It is always perpendicular to the wavefronts of the light. In most places, these rays travel in straight lines. This helps us understand how light moves through different tools.

There are different ways a ray can act when it hits something. An incident ray is a ray that strikes a surface. It might bounce off, which is called reflection. The Law of Reflection says the angle of reflection equals the angle of incidence. A ray can also pass through a surface. This is called a transmitted ray, or refraction. The amount of energy must stay the same. It is either reflected, transmitted, or absorbed by the surface.

Researchers use math to track these rays through complex systems. This method is called ray tracing. It uses rules to see how rays move through lenses and mirrors. This works well when objects are much larger than the light's wavelength. Ray tracing helps computers simulate how very complex optical systems work. It can even help find where a real or virtual image will form.

This makes it easier to design new tools.

Different types of rays help scientists study specific parts of a system. A marginal ray starts at an object point and touches the edge of an aperture. A chief ray starts at the edge of an object and passes through the center.

These rays help define the size of an image. Some rays are called paraxial rays because they stay close to the center axis. Other rays, called skew rays, do not stay in a flat plane. These details help experts understand how much light a system can carry.

You can see these ideas in things like fiber optics. Fiber optics are thin wires that carry light. Inside these fibers, some rays are called guided rays. These rays stay trapped inside the core of the fiber. They move in paths that keep them from escaping. This is how light travels through long cables to send information. Understanding rays helps us build the technology we use every day.

In the study of optics, a ray is an idealized geometrical model used to represent light.

While light actually moves as electromagnetic waves, scientists use rays to simplify how we view its movement. A ray is defined as a line that is perpendicular to the light's wavefronts. It points in the specific direction of energy flow. This model is incredibly useful because it allows us to treat light as discrete paths. By doing this, we can use mathematical tools to analyze how light travels through complex optical systems.

To understand how rays work, we must look at how they interact with different materials. When a ray strikes a surface, it is called an incident ray. The angle between this ray and the perpendicular line to the surface is the angle of incidence. If the ray bounces off the surface, it becomes a reflected ray. According to the Law of Reflection, the angle of reflection is always equal to the angle of incidence for non-scattering surfaces. If the light passes through the surface instead, it is called a transmitted ray. The angle of this new path is known as the angle of refraction, which is determined by Snell's law. During this process, the total power must be conserved. The power in the incident ray must equal the sum of the power in the reflected ray, the refracted ray, and any power absorbed by the surface.

Optical systems use many specific types of rays to help scientists model how images are formed. One important type is the marginal ray, which is also called an a-ray. This ray starts at a point on the optical axis and touches the edge of the system's aperture stop. Marginal rays are vital because they help locate where a real or virtual image will form. Another key type is the chief ray, or b-ray. This ray starts at the edge of an object and passes through the center of the aperture stop. Together, the marginal and chief rays define the Lagrange invariant. This value characterizes the throughput, or etendue, of the entire optical system.

Scientists also categorize rays based on the geometric planes they inhabit. A meridional ray, or tangential ray, stays within a single plane that contains both the object point and the system's optical axis. This specific plane is called the meridional or tangential plane. In contrast, a skew ray does not stay in such a plane. Skew rays do not cross the optical axis and are not parallel to it. There are also sagittal rays, which propagate in a plane perpendicular to the meridional plane. The principal ray is unique because it serves as both a sagittal and a meridional ray.

In many calculations, researchers use a simplified method called the paraxial approximation. This involves modeling paraxial rays, which are rays that make small angles to the optical axis. These rays stay very close to the axis throughout the entire system. However, when more precision is needed, scientists use finite rays or real rays. These are traced without using the paraxial approximation. In systems that lack symmetry around the optical axis, researchers might use parabasal rays. These rays propagate close to a defined base ray rather than the central axis. This allows for more accurate computer modeling of complex real-world systems.

The concept of the pupil is also central to ray modeling. The entrance pupil is an image of the aperture stop formed by the optics located in front of it. Its size and location are determined by chief and marginal rays. Similarly, the exit pupil is the image of the aperture stop formed by the optics behind it.

Understanding these pupils helps engineers determine how much light can pass through a lens system and how large the resulting image will appear.

Ray modeling is also essential for understanding technology like fiber optics. In an optical fiber, rays can behave in several distinct ways. A meridional ray passes directly through the axis of the fiber. A skew ray travels in a non-planar, zig-zag path and never crosses that central axis. Some rays are considered guided, bound, or trapped rays. These rays are confined within the core of a multi-mode fiber. However, some light can be lost through leaky or tunneling rays. These occur when the curved boundary of a core causes light to escape, even when geometric optics predicts it should reflect perfectly. This detailed understanding of ray behavior allows for the creation of high-speed communication technologies used globally.