Flashcards in Waves Deck (49)

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1

## What is a PROGRESSIVE WAVE?

### It moves energy from one place to another without transferring any matter

2

## How does a WAVE work?

### Either matter or a field oscillates at a source, which passes through a medium or field when it oscillates which takes energy away from the source

3

## Describe a reflection

### When a wave is bounced back when it hits a boundary

4

## Describe a refraction

### When the wave changes direction as it enters a different medium - as a result of the wave slowing down or speeding up

5

## Describe a diffraction

### When the wave spreads out as it passes through a gap or round an obstacle

6

## What is displacement in terms of waves?

### How far a point on a wave has moved from its undisturbed position

7

## What is amplitude in terms of waves?

### The maximum magnitude of displacement that a wave can be from an undisturbed position.

8

## What is wavelength in terms of waves?

### The length of one whole oscillation (length between two whole crests or two equal point on a wave)

9

## What is a period in terms of waves?

### The time taken for one whole wave cycle

10

## What is frequency in terms of waves?

### The number of whole waves passing a certain point per second

11

## What is a phase in terms of waves?

### A measurement of the position of a certain point along the wave cycle

12

## What is phase difference in terms of wave?

###
The amount which one wave lags behind another wave

can be measure in degrees, radians, or fractions of a cycle

13

## What is the equation for FREQUENCY?

###
frequency=1/time(or period)

f(Hz) = 1

-----

T(s)

14

## What is the equation for WAVE SPEED

###
Wave speed = frequency x wavelength

or wave speed = distance/time

c(ms^-1)=f(Hz) x lambda(m)

15

## What is the speed of an EM wave is a vacuum?

### 3 x 10^8 (ms^-1)

16

## How could you measure the speed of a wave in water?

###
1. Set up a ripple tank with a strobe light over it with a signal generator and a ripple tank dipper

2. Measure the depth of the water, then set the dipper to a frequency with regular vibrations

3. Dim the rooms light and match the strobe light frequency so that the waves appear to be standing still

4. Record the frequency on the signal generator and the distance between adjacent peaks and then dividing it by the amount of troughs in between them

5. Then use the equation c=f x wl to calculate the wave speed

17

## What is a TRANSVERSE WAVE?

### It is a wave that oscillates particles or the field perpendicular to the direction of travel

18

## How could you draw a transverse wave on a graph?

###
Displacement against time

or

Displacement against distance

19

## What is a LONGITUDINAL WAVE?

### It is a wave that oscillates particles or the field parallel to the direction of travel

20

## What is a polarising filter?

### A filter that only lets light waves oscillate through it in one direction - so if you had two filters at right angles to each other no light could pass through

21

## What are the uses for polarising filters?

###
To reduce glare in sunglasses

To improve TV and radio signals

22

## When does superposition occur?

### When two or more waves pass through each other - the displacements in each wave combine

23

## What is constructive inference?

### When waves meet and their displacements are in the same direction they combine to make a larger net displacement

24

## What is destructive interference?

### When waves meet and the positive displacement of one wave meets a wave with a negative displacement of another wave and cancel each other out

25

## What is total destructive interference?

### When two waves of equal and opposite displacements meet and completely cancel each other out

26

## What is a stationary wave?

### When two progressive waves superposition and they have the same frequency(or wavelength) and amplitude and are moving in opposite directions

27

## Do stationary waves transmit energy?

### NO

28

## What is a resonant frequency?

### When a source produces an exact number of waves in the time it takes a wave to get to be reflected

29

## What does a resonant frequency cause on a string?

### A stationary wave where the pattern does not move it just vibrates up and down

30