Definition of wavefront
If you throw a stone into a pool of water, circular water waves moving away from the center of the circle. In the water waves, there are crests and troughs. Wave peaks or waves valleys that move away from the center of the circle can be said as a wavefront.
Two adjacent wavefronts are two parts of the wave that has the same phase and are separated by one wavelength. Wave peaks or wave valleys that have the same phase and are separated by one or more wavelengths are referred to as wavefronts. In addition to water waves, sound waves or light waves also have a wavefront. In contrast to water waves that move only in a plane or area, sound waves and light waves move in space.
Definition of ray
Rays are imaginary lines perpendicular to the wavefront. The concept of the ray is used to explain the direction of wave propagation.
Definition of the beam of light
An object can be seen because it emits light or reflects light emitted by other objects. For example, candlelight, neon lights, and the sun can be seen because they can emit light. The moon can be viewed because it reflects sunlight, while the book that we read or the food can be seen because books and food reflect sunlight. Objects such as books and food cannot be seen if there is no light reflected by the object.
When looking at an object, light moves from object to eye through a straight line. For example, a book is in front of you. You of course only see the front of the book and the side of the book where the reflected light moves straight towards your eyes. You cannot see the bottom of the book.
The beam of lights means a collection of light. The book in front of you reflects the beam of light in all directions. Because light cannot turn, only parts of the object where light is possible to move straight towards the eye that can be seen. Only certain parts of the object can be seen because only specific light beams are reflected by objects, moving straight up to the eye. In connection with light, a small set of beams of light emitted or reflected by an object can be described in the form of a ray.