Diffraction interference patterns with phasor diagrams

Summary

This video explores the phenomenon of wave interference and diffraction, explaining how waves interact with barriers, especially those with holes. It demonstrates how a single or multiple holes can create interference patterns, showing how the size of the hole affects the wave's behavior. With smaller holes, waves spread out more, while larger holes cause less diffraction, resulting in a more direct wave path. The video also explains the relationship between the phase difference of waves and the resulting amplitude, providing insight into how these interactions create striking interference patterns.

Takeaways

• 😀 A wave passing through a wall with two holes creates a striped interference pattern.
• 😀 Even a single hole can create an interference pattern, but the pattern depends on the hole size and wavelength.
• 😀 Waves can be thought of as a combination of infinite smaller waves spreading out in all directions.
• 😀 When a wave hits a small hole, only the portion behind the hole can pass through, causing the wave to spread out.
• 😀 A larger hole allows more of the wave to pass through, creating the possibility for interference among the waves.
• 😀 The interference pattern from two holes results from the combination of sine waves that are either in phase or out of phase.
• 😀 When two sine waves are in phase, their amplitudes add together, creating constructive interference.
• 😀 The phase difference between two waves depends on the distance from the two holes and the angle of observation.
• 😀 As the phase difference increases, the interference pattern’s amplitude can either increase or decrease, creating the striped pattern.
• 😀 A single large hole can be thought of as many small holes, and the interference pattern produced is similar to that of multiple smaller holes.
• 😀 For very large holes relative to the wavelength, the wave does not spread out but travels in a more straight-line manner.
• 😀 The amplitude of the wave passing through a large hole decreases rapidly as the angle of observation changes, producing a weaker interference effect.
• 😀 The size of the hole in relation to the wavelength determines whether the wave spreads out or remains more focused.
• 😀 For more detailed information on waves and their behavior, the video suggests checking additional content on the channel.

Q & A

What happens when a wave passes through a wall with two holes?

When a wave passes through a wall with two holes, an interference pattern is created. This occurs because the waves coming out of each hole interact with each other, either reinforcing or canceling each other out depending on their phase.

Can an interference pattern be created with just one hole?

Yes, an interference pattern can also be created with just a single hole. This happens because a single hole can be thought of as many small holes next to each other, each emitting a wave, and these waves interfere with each other.

How does the size of the hole affect the behavior of the wave?

The size of the hole affects how much of the wave passes through and how much the wave spreads out. A smaller hole causes the wave to spread out more, while a larger hole results in less spreading and a more direct wave path.

What role do smaller waves play in wave interference?

Each wave can be thought of as the combination of an infinite number of smaller waves spreading out in all directions. These smaller waves interact with each other to form an interference pattern when they pass through a hole or a set of holes.

Why do waves spread out when passing through a small hole?

Waves spread out when passing through a small hole because only the part of the wave directly behind the hole can pass through. This causes the wave to diffract and spread out as it travels beyond the hole.

What is meant by waves being 'in phase'?

Waves are 'in phase' when the peaks of two sine waves occur at the same time. This results in constructive interference, where the amplitudes of the waves add together to form a larger wave.

How does the distance between two holes affect the interference pattern?

The distance between the two holes affects the phase difference between the waves emitted from them. As the distance between the holes increases, the phase difference increases, which in turn affects the strength and nature of the interference pattern.

What happens to the amplitude of the wave as the angle of observation changes?

As the angle of observation changes, the difference in phase between the two sine waves increases, causing the amplitude of the resulting wave to fluctuate. The amplitude can range from a large value to zero depending on the phase relationship between the waves.

How does a single large hole create an interference pattern?

A single large hole can be thought of as a collection of many small holes next to each other. Each small hole generates a sine wave, and these waves combine, leading to an interference pattern. The phase differences between the waves cause the amplitude of the resulting wave to fluctuate.

Why does the interference pattern become weaker with larger holes?

With larger holes, the waves emitted from the small holes within the larger hole have very small phase differences. This causes the amplitude of the resulting wave to decrease rapidly as the angle changes, making the interference pattern weaker and less pronounced.