# A lot of questions about wave optics

• haha1234
In summary, the conversation discusses how interference can occur with parallel rays of light incident on a surface. The concept of multiple parallel lights is introduced, and the idea of combining electric fields and resulting constructive or destructive interference is explained. This can be understood by imagining the waves as extended and infinite, with "rays" representing the direction of travel.
haha1234

## Homework Statement

In this picture,the ray b and c are parallel.So why there are interference occur?

## The Attempt at a Solution

You can't think of it as one single ray of light. You must think of lots of parallel lights incident on the surface. Can you see how interference will occur then?

BOYLANATOR said:
You can't think of it as one single ray of light. You must think of lots of parallel lights incident on the surface. Can you see how interference will occur then?

Sorry,I don't understand. Although there is a lot of rays,they are parallel thus they cannot combine.So I cannot imagine how interference can occur.

The light waves are extended, similarly to water waves in the picture: crests and troughs traveling in a certain direction. They can be imagined of infinite extension, - infinite with respect to the wavelength. A "ray" represents a normal of such "wavefronts", showing the direction of travel of the wave. You can draw a ray everywhere.

The wave reflected from the first surface of the layer is also a wave with its crests and troughs, and there is an other wave reflected from the back surface of the layer. There is some electric field corresponding to both reflected ways. These fields combine (interfere) making the resultant reflected wave. If the crests of the first reflected wave coincide with crests of the second wave, they intensify each other, (constructive interference). When the crest of the first reflected wave coincide with troughs of the second one, the resultant wave is weak, it is destructive interference.

ehild

#### Attachments

• wavefronts.JPG
30.3 KB · Views: 411
• waveinterference.JPG
10.1 KB · Views: 456
1 person

Interference occurs when two or more waves interact with each other, resulting in a change in the amplitude, frequency, or phase of the resulting wave. In the case of the two parallel rays, b and c, they may have different amplitudes, frequencies, or phases, which can lead to interference when they overlap. This can be seen in the picture, where the two rays are overlapping and creating a pattern of light and dark bands, indicating constructive and destructive interference. This phenomenon is known as Young's double-slit experiment and is a fundamental concept in wave optics. It is also important to note that even when rays are parallel, they can still have slight differences in their properties, leading to interference.

## 1. What is the difference between wave optics and geometric optics?

Wave optics and geometric optics are two different branches of optics that study the behavior of light. Geometric optics deals with the propagation of light as rays, while wave optics considers light as a wave phenomenon. Geometric optics is used for understanding simple optical systems, while wave optics is used for more complex systems where the wave nature of light cannot be ignored.

## 2. What are the properties of a wave?

A wave is characterized by several properties, including wavelength, amplitude, frequency, and velocity. Wavelength is the distance between two consecutive crests or troughs of a wave. Amplitude is the height of the wave from its baseline. Frequency is the number of wave cycles that pass a given point in one second. Velocity is the speed at which the wave propagates through a medium.

## 3. What is the principle of superposition in wave optics?

The principle of superposition states that when two or more waves interact, the resulting wave is the sum of the individual waves. This principle is essential in wave optics as it explains phenomena such as interference and diffraction. It also allows us to analyze the behavior of waves in complex systems.

## 4. What is diffraction in wave optics?

Diffraction is the bending of waves around obstacles or through small openings. In wave optics, it refers to the phenomenon where light waves spread out as they pass through a narrow opening or around an obstacle. Diffraction is the reason why we can see objects around corners or why sound can travel through walls.

## 5. How is the speed of light related to the refractive index?

The refractive index of a material is a measure of how much the speed of light slows down when passing through that material. It is directly related to the speed of light in a vacuum, which is the fastest possible speed for light. The higher the refractive index, the slower the speed of light in that material. This relationship is described by Snell's Law, which governs the behavior of light at the interface of two different materials.

Replies
5
Views
1K
Replies
3
Views
1K
Replies
1
Views
1K
Replies
1
Views
1K
Replies
9
Views
6K
Replies
2
Views
1K
Replies
27
Views
673
Replies
1
Views
983
Replies
2
Views
4K
Replies
1
Views
1K