Progressive and stationary waves

Question 1

displacement

Answer 1

distance and direction an oscillating particle moves from its rest position
metre (m)

Question 2

amplitude A

Answer 2

maximum displacement an oscillating particle in the medium moves from its rest position
metre (m)

Question 3

wavelength , lambda

Answer 3

distance between any point on a wave to an adjacent one that is exactly in phase with it
metre (m)

Question 4

period T

Answer 4

time taken for one complete wave to pass a fixed point
second (s)

Question 5

frequencyf

Answer 5

number of complete
waves passing a fixed point per second
hertz (Hz)

Question 6

define the PHASE of a particle on a wave

Answer 6

the phase of a particle on a wave is the fraction of a cycle it has completed since the start of the cycle.

Question 7

define the PHASE DIFFERENCE of two particles?

Answer 7

the phase difference of two particles on a wave, or on two waves is the fraction of a cycle by which their oscillations are separated.

Question 8

what can phase difference be expressed in?

Answer 8

-fraction of the wavelength, lambda
-in degrees
-in radians

Question 9

how many degrees and radians is 1 cycle?

Answer 9

1 cycle or 1 lambda = 360° = 2 π radians

Question 10

if two points on a wave are separated by a horizontal distance, d ….. what’s is the phase difference in radians?

Answer 10

phase difference in radians= 2 πd/ wavelength

ONLY FOR PROGRESSIVE WAVES

Question 11

what is a WAVEFRONT ?

Answer 11

a wavefront is a line or a surface on which the vibrations of the medium all have the same phase at all points.

Question 12

how to convert between degrees and radians?

Answer 12

x 180/π
____>

π = 180

< ____
x π/180

Question 13

how many degrees is 1 radian?

Answer 13

360° = 2 π radians
360°/ 2π = 1 radian
57.3° = 1 radian

Question 14

how many radians is 90°?

Answer 14

π / 2

Question 15

how many radians is 180°?

Answer 15

π

Question 16

how many radians is 270° ?

Answer 16

3 π/ 2

Question 17

how many radians is 360° ?

Answer 17

2 π

Question 18

what are waves caused by?

Answer 18

Waves are caused by something oscillating the particles in the medium (or oscillating the field) through which the wave travels.

Question 19

what is a PROGRESSIVE wave?

Answer 19

A progressive wave transfers energy from one place to another without transferring matter.

Question 20

what equation are frequency and period related by

Answer 20

f= 1/T

Question 21

what equation are the speed, frequency and wavelength of a wave related?

Answer 21

wave speed c = f x lambda

Question 22

what are mechanical waves?

Answer 22

Mechanical waves require a physical substance to move through.

Question 23

what are electromagnetic waves?

Answer 23

Electromagnetic waves can travel through a vacuum - they are oscillations in electric and magnetic fields that permeate space. All electromagnetic waves travel at the same speed in a vacuum:
3.00X109 m/s

Question 24

what are longitudinal waves?

Answer 24

Longitudinal waves - oscillations of the medium are parallel to the direction of energy transfer. For example, sound waves.

Question 25

what are transverse waves?

Answer 25

Transverse waves - oscillations of the medium are perpendicular to the direction of energy transfer. For example, electromagnetic waves and waves on a string.

Question 26

what is the principle of superposition?

Answer 26

The principle of superposition states that when two waves meet, the total displacement at a point is equal to the sum of the individual displacements at that point.

Question 27

what is reinforcement?

Answer 27

It two waves meet exactly in phase, they will add together CONSTRUCTIVELY to form a double height wave (reinforcement)

Question 28

what is cancellation?

Answer 28

It two waves meet exactly out of phase (antiphase), they will add together DESTRUCTIVELY and cancel each other out

Question 29

what is polarisation?

Answer 29

when the oscillation of a a transverse wave are restricted into a single plane, they are polarised.

Question 30

if a wave can be polarised, it must be…

Answer 30

a transverse wave (longitudinal waves can’t be polarised)

Question 31

how do transverse waves passing through a slit on a board become polarised?

Answer 31

only oscillations parallel to the slit pass through it

Question 32

how are glares caused?

Answer 32

Light reflected from some surfaces (wate/ glan) is partially polarised. this reflected light causes glare.

Question 33

how can glare be reduced?

Answer 33

by filtering out the polarised light using polarising filters

Question 34

how is a stationary wave formed?

Answer 34

A stationary wave is formed when two progressive waves with the same frequency and amplitude, moving in opposite directions, superpose.

Question 35

how are stationary waves most commonly formed?

Answer 35

Stationary waves are often the result of the reflection of a progressive wave superposing with the original wave.

Question 36

what is a node?

Answer 36

A node is a point where there is no oscillation - the two waves always meet with a phase difference of 180° (pi radians).

Question 37

what is antinode?

Answer 37

An antinode is a point where oscillation is at maximum amplitude - the two waves always meet in phase at that point.

Question 38

distance between two nodes in a stationary wave is

Answer 38

distance between two node = 1/2 wavelength

Question 39

what does it mean when all the point between two nosed oscillate in phase…

Answer 39

All the points between two nodes oscillate in phase, meaning they reach their maximum displacements at the same time.

Question 40

do stationary waves that oscillate freely transfer energy to their surrounding?

Answer 40

Stationary waves that oscillate freely do not transfer energy to their surroundings. When stationary waves are formed: • by sound waves, there is silence at the nodes and maximum volume at the antinodes • in a microwave oven, there is no heating at the nodes, and maximum heating at the antinodes.

Question 41

describe the first harmonic

Answer 41

The first harmonic: As the frequency of oscillation is increased from zero, the first harmonic is seen at the lowest frequency that gives a pattern.

Question 42

what equation is The frequency f of the first harmonic related to the length l, tension T, and mass per unit length u of the string by ?

Answer 42

f = 1/2 l square root (T/u)

Question 43

describe the second and third harmonic….

Answer 43

The second harmonic occurs at twice the frequency of the first harmonic; the third harmonic occurs at three times the frequency of the first harmonic; etc.

Question 44

what is the wavelength and frequency at the first harmonic?

Answer 44

wavelength= 2L (length of string) frequency= f0

Question 45

what is the wavelength and frequency at the second harmonic?

Answer 45

wavelength= L frequency= 2f0

Question 46

what is the wavelength and frequency at the third harmonic?

Answer 46

wavelength = 2L/3 frequency = 3f0