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Wavefront is an imaginary surface representing the corresponding points of a wave that vibrate in unison.
- It is the collection of all points that share the same phase.
- Locus is the path taken by a specific point originating from the light source.
- All the sites undergo locus, which results in different wavefront forms.
Waves are represented using only an oscillating sine function. This representation works well for one-dimensional waves, however, it becomes challenging for waves in two or more dimensions. Thus, the concept of wavefronts was introduced.
Read More: NCERT Solutions for Class 12 Physics Wave Optics
Key Terms: Wavefront, Waves, Motion, Locus, Light, Spherical Wavefront, Cylindrical Wavefront, Plane Wavefront
What is Wavefront?
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A wavefront is a hypothetical surface that shows identical wave points vibrating in unison.
- The collection of all points in a medium where a wave is experiencing the very same period is known as a wavefront.
- This could be the location of all the crests, all the troughs, or any intermediate phase.
- Wavefronts can be used to visualize the two-dimensional wave motion.
- One wavelength refers to the distance between any two lines on a wavefront.
- To put it simply, a wavefront is the collection of all the endpoints that belong to a single phase.
Example of Wavefront
- Suppose, waves propagate from the point of impact a small stone is dropped into a still pool of water.
- Gradually, every point on the ground begins to oscillate.
- A snapshot of the ground at any one time would capture the circular rings where the disturbance is greatest.
- Since each point on a circle is at the same distance to the source, it is obvious that they are all oscillating in phase.
- Thus, a wavefront is a group of points that oscillate in phase, and it is described as a surface with continuous phase.
![Wavefront]()
Wavefront
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History of Wavefront
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Christian Huygens initiated a ground-breaking tech revolution in the 17th century. He suggested that light actually flows as waves and is a kind of energy.
- He offered an explanation by stating that every power system of light emits light waves simultaneously throughout all areas in three dimensions.
- Underneath the impact of wave power, the particles in its vicinity move on a regular basis.
- The points from a specific place are available in this kind of propagation at the same period in regard to time.
- A wavefront is a surface created by this cluster of points or particles that are in phase with one another.
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Types of Wavefronts
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The various types of wavefronts are determined by the path followed by the particles emanating from a source.
There are mainly three types of wavefronts namely
- Spherical Wavefront
- Cylindrical Wavefront
- Plane Wavefront
Spherical Wavefront
Wavefronts that appear as spheres centered on the origin are known as spherical wavefronts.
- When the source of the light is a prime source, a spherical wavefront will be created.
- Point source denotes a source of light that is so little that it can only be described as a point.
- It is conceivable without dimensions.
Examples of spherical wavefronts are
- Ripples in water, for instance, are represented as spherical wavefronts that are concentric rings.
- In a vacuum-like space, electromagnetic radiation produces a spherical wavefront.
- The creation of concentric rings when a stone is thrown into water is another example.
![Types of wave front]()
Types of Wavefront
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Cylindrical Wavefront
Cylindrical wavefronts are produced by an expanded linear source, such as a small slit-like aperture.
- On a cylinder's curved surface are all the locations that are equal to the distance from the source. As a result, the wavefront has a cylindrical shape.
- But if we sketch the wavefront from only one surface, it resembles a concentric circle.
- In simple terms, we get a cylindrical wavefront from a linear source of light.
Examples of the cylindrical wavefront are
- Light rays from one lens that strike another lens collide at a specific spot.
- It assumes the shape of a cylinder as they twist and merge at a particular place.
- A cylindrical wavefront is emitted by a tube light.
Plane Wavefront
The term "planar wavefront" refers to a wavefront that originates from an infinitely distant point source of light.
- When observed from a significant distance away from an origin of any kind, the wavefront will look like a plane.
- A wavefront of this type is known as a plane wavefront.
- Additionally, the plane wavefront is produced when a tiny portion of a remote point, such as infinity, generates a spherical or cylindrical wavefront.
- A plane wavefront is created when sunlight from the Sun strikes the Earth's surface.
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Applications of Wavefront
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The various applications of the wavefront are as follows:
- Wavefront analysis can utilize the information to determine image quality with a number of determining metrics, including the point spreading function (PSF), Strehl ratio, and modulation linear transfer, in addition to providing the optical system defects.
- The quickest, easiest, and most efficient way to correct refractive problems in the naked eye is by using wavefront LASIK.
- It is a medical technique that reshapes the cornea and enhances visual clarity using directed lasers.
- It is also used in the treatment of hypermetropia, astigmatism, and myopia.
Things to Remember
- Wavefront is the collection of all locations in a medium that have the same period as a wave.
- It is also defined as a surface with a continuous phase and is made up of a collection of points that oscillate in phase.
- Wavefronts can be classified as spherical, cylindrical, or planar wavelengths.
- A spherical wavefront is produced when a main source of light is used.
- Cylindrical wavefront emerges from a straight light source.
- The wavefront will appear to be a plane when viewed from a sufficient distance away from an origin of any kind.
Previous Years’ Questions
- Wavefront of a wave has a direction with wave motion…
- Wavefront is the locus of all points, where the particles… (KCET 2011)
- Spherical wavefronts, emanating from a point source… (JKCET 2012)
- Two plane wavefronts of light, one incident on a thin convex lens… (KEAM)
- In the adjacent diagram, CP represents a wavefront, and AO… (JEE Advanced 2003)
- The wave theory of light was given by… (JKCET 2004)
- In which of the following the interference is…
- A wave has velocity v in medium P and velocity 2v in medium… (BITSAT 2007)
- A white source of light during interference forms only… (AIIMS 2007)
- The wavelength of electromagnetic waves produced…
Sample Questions
Ques. What is Wavefront in Physics? (2 Marks)
Ans. Wavefront is an imaginary surface that shows identical wave points vibrating in synchrony. The collection of all the points in the same phase is known as a wavefront.
Ques. How is Wavefront used in medical facilities? (3 Marks)
Ans. Wavefront aberration in an optical system is the departure of a wavefront from the ideal planar wavefront. Typically, wavefront aberrations are defined as a collection of two-dimensional polynomial terms and the sampled image. By adopting guided procedures like Wavefront-guided LASIK, these aberrations can be reduced for a variety of optical system applications.
Ques. What are the types of Wavefronts? (2 Marks)
Ans. There are three different forms of wavefronts:
- Spherical Wavefront
- Cylindrical Wavefront
- Plane Wavefront
They are differentiated by the path that the particles leaving a source take.
Ques. Give the relationship between path difference and wavelength for two waves experiencing constructive interference. (1 Mark)
Ans. The path difference between two waves must be an integral multiple in order for there to be constructive interference, which means that p = n, where n = 0, 1, 2, 3,...., etc.
Ques. What is Wavefront LASIK? (3 Marks)
Ans. Wavefront LASIK is the quickest, simplest, and most effective treatment for refractive errors in the human eye. Wavefront LASIK is a medical process that employs guided lasers to reshape the cornea and improve visual sharpness. It lessens the side effects related to the traditional LASIK. It helps to treat Myopia or Nearsightedness, Astigmatism, and Hypermetropia.
Ques. What kind of wavefront is spherical? (1 Mark)
Ans. Concentric circles that form when a stone is thrown into water are an example of spherical wavefronts.
Ques. What is Wavefront Aberration? (3 Marks)
Ans. Wavefront Aberration is the deviation of a wavefront from the perfect planar wavefront in an optical system. Wavefront aberrations are usually represented as both the sampled image and the collection of 2-D polynomial terms. These aberrations can be minimized in optical systems only by using guided treatments like Wavefront-guided LASIK.
Ques. What distinguishes a wavefront from a ray? (1 Mark)
Ans. A wavefront is a surface created by connecting all vibrationally synchronous points. A ray is a line drawn in the direction of the propagation of light waves that is perpendicular to the wavefront.
Ques. What does a wavefront in a plane mean? (1 Mark)
Ans. The rays emanating from the sun are a typical illustration of the planar wavefront.
Ques. What is Optics? (2 Marks)
Ans. Optics is defined as the study of the properties and behavior of light. It is the study of the phenomenon of different types of light such as visible light, Infrared light, and Ultraviolet rays among others. It also deals with the concepts of reflection and refraction.
Ques. A red light beam is used to create a diffraction pattern. What would happen if blue light were to take the place of red light? Bands may
(a) vanish
(b) grow wider and farther apart
(c) remain unchanged.
(d) Diffraction bands get smaller and cluster closer together. (2 Marks)
Ans. (d) Diffraction bands get smaller and cluster closer together.
We know that blue light has a shorter wavelength than red light. Thus, the diffraction bands consequently get smaller and closer together.
Ques. What two key changes in the single-diffraction slit's pattern will you see when a white light source takes the place of the monochromatic one? (3 Marks)
Ans. The diffraction pattern changes as follows when a white light source is used in place of a monochromatic source.
- The diffracted picture of the slit is divided into individual hues of white light in each diffraction order. Since fringe width and wavelength are inversely related, the violet fringe has a smaller wavelength and is wider than the red fringe.
- The dispersion is greater in higher-order spectra, which results in color overlapping.
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