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Flashcards in Wave Properties Deck (18)
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1
Q

When does diffraction occur?

A

Diffraction occurs when waves spread out after passing through a gap or around an obstacle.

2
Q

What are some features of diffraction?

A
  • The narrower the gap, the more the waves spread out.

* The longer the wavelength the more the waves spread out.

3
Q

What is diffraction?

A

The way that waves spread out as they come through a narrow gap or go round obstacles.

4
Q

What does the amount of diffraction depend on?wavelengths wide.
• Most diffraction occurs when the gap is the same size as the wavelength

A

The amount of diffraction depends on the wavelength of the wave compared with the size of the gap.
• When the gap is bigger than the wavelength, diffraction is unnoticeable.
• Noticeable diffraction occurs through a gap several wavelengths wide.
• Most diffraction occurs when the gap is the same size as the wavelength
• If the gap is smaller than the wavelength, the waves are mostly reflected back.

5
Q

What happens when the gap is bigger than the wavelength?

A

Diffraction is unnoticeable.

6
Q

When do you get noticeable diffraction?

A

• Noticeable diffraction occurs through a gap several wavelengths wide.

7
Q

When does the most diffraction occur?

A

• Most diffraction occurs when the gap is the same size as the wavelength

8
Q

What happens if the gap is smaller than the wavelength?

A

• If the gap is smaller than the wavelength, the waves are mostly reflected back.

9
Q

What is required to view a clear diffraction pattern for light?

A

You need a monochromatic, coherent light source.

10
Q

What does monochromatic mean?

A

All the light has the same wavelength and frequency, and also therefore is the same colour.

11
Q

Why do waves diffract?

A
  • Each point on a wavefront is a secondary emitted of wavelets.
  • The wavelets from the point along a wavefront travel only in the direction in which the wave is travelling, not in the reverse direction.
  • They then combine to form a new wavefront spreading beyond the gap.
12
Q

What is a wavefront?

A

A wavefront is a line or surface, in the path of a wave motion, where all the displacements at any point have the same phase

13
Q

What is reflection?

A

When straight waves directed a certain angle to hard flat surface, reflect off at the same angle.

14
Q

What is the angle between the reflected wavefront and the surface equal to?

A
  • Angle between the reflected wavefront and the surface is the same as between the incident wavefront and the surface.
  • Direction of the reflected wave is at the same angle to the reflector as the direction of the incident wave.
15
Q

What is a feature of the direction of a reflected wave?

A

• Direction of the reflected wave is at the same angle to the reflector as the direction of the incident wave.

16
Q

What happens when waves pass across a boundary at which the wave speed changes?

A

When the wave speed changes, the wavelength also changes.

17
Q

What happens if the wave-fronts approach at an angle to the boundary?

A

They change direction, speed and wavelength.

18
Q

What is refraction?

A

When waves change direction, speed and wavelength as they pass through a boundary.