/ Preparation Physics Wave Optics
Under the chapter “wave optics”, there comes a concept called addition of waves. Let us understand this through an example. When two or more than two waves meet each other in the space, they will combine to form another new wave. This phenomenon is called superposition. However, the type of this combination can also vary depending on factors such as the nature of the phase i.e. how the wave peaks and troughs will overlap with each other. There are mainly 2 types of these combinations:
- Coherent Addition of Waves
- Incoherent Addition of Waves
Let us understand these categories briefly through the article given below.
- Types of Addition of Waves
- Coherent Addition of Waves
- Constructive Interference
- Destructive Interference
- Incoherent Addition of Waves
- Physics Class 12 NCERT Solutions
Types of Addition of Waves
Understanding the core concepts of coherent and incoherent addition of waves are extremely crucial for candidates who are aspiring to prepare for JEE MAINS. These fundamentals help develop the foundations of wave optics and quantum mechanics.
Here’s a quick comparison between these two which can help you understand the basic mechanism of addition of waves:
Coherent Addition of Waves
Coherent waves are the types of waves who have a constant phase difference i.e. the peaks and troughs of the wave perfectly overlap with each other in a predictable way over a particular time period. These waves have almost the same frequency and are generally emitted by the same source or synchronized sources. Example: laser beam.
Mathematically, if 2 waves have the same amplitude, the resultant value can be denoted by:
2Acos(ϕ/2)
Where,
A = Amplitude
Φ = Phase difference
As a result, the interference pattern is stable in this case.
Constructive Interference
This is the type of interference that occurs when the crest of one wave aligns with the crest of another, due to which amplitude increases.
Destructive Interference
This is the type of interference that occurs when the crest of one wave meets the trough of the other, due to which amplitude decreases.
Incoherent Addition of Waves
Incoherent waves are another category of waves that occur when the waves have rapidly varying phase differences i.e. their peaks and troughs do not align with each other. The frequencies of these waves differ and are usually emitted from independent sources. Example: lights from 2 different bulbs.
So if 2 waves of different intensities are added, the answer is:
I (total) = I1+I2
As a result, there is no stable interference pattern in this case.
Physics Class 12 NCERT Solutions
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Commonly asked questions
What is the meaning of the term interference in diffraction?
Interference is a concept that forms the base of diffraction, without which diffraction is not practically possible. The waves formed by diffraction form secondary waves which either cross each other, move in directions opposite to each other, or overlap each other. This situation creates some alternating bright and dark fringes called interference.
Can we convert a coherent wave into an incoherent wave (or vice versa)?
Yes, whether a wave is coherent or incoherent depends on its phase difference and frequency. For converting a coherent wave into an incoherent wave, you have to damage the stable phase of the wave. This can be done by making the medium tough or mixing them with incoherent waves.
Similarly, incoherent waves can be converted into coherent waves by making their frequencies same and having all of them into the same phase.
Are coherent and incoherent waves visible to the human eye?
Yes, both coherent and incoherent waves can be seen by the naked eye. However, we cannot detect whether the wave is coherent or incoherent. This is because the incoherent waves have different frequencies which cannot be distinguished by the human eye. We have can only see lights of specific wavelengths as per the human limit.
Physics Wave Optics Exam
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