Flashcards in Wave Properties Deck (18):

1

## When does diffraction occur?

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

2

## What are some features of diffraction?

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

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

3

## What is diffraction?

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

4

##
What does the amount of diffraction depend on?wavelengths wide.

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

###
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

## What happens when the gap is bigger than the wavelength?

###
Diffraction is unnoticeable.

6

## When do you get noticeable diffraction?

### • Noticeable diffraction occurs through a gap several wavelengths wide.

7

## When does the most diffraction occur?

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

8

## What happens if the gap is smaller than the wavelength?

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

9

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

### You need a monochromatic, coherent light source.

10

## What does monochromatic mean?

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

11

## Why do waves diffract?

###
• 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

## What is a wavefront?

### 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

## What is reflection?

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

14

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

###
• 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

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

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

16

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

### When the wave speed changes, the wavelength also changes.

17

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

### They change direction, speed and wavelength.

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