physics - waves

Question 1

what are the 2 types of waves

Answer 1

mechanical and electromagnetic waves

Question 2

what is the definition of a mechanical waves and give examples

Answer 2

a mechanical wave needs a medium.
examples : waves on a guitar string , water waves , seismic waves.

Question 3

what is the definition of an electromagnetic waves and give exampled

Answer 3

the electromagnetic wave does not need a medium.
examples : radio waves , infrared , ultraviolet.

Question 4

what is the definition of a longitudinal wave ?

Answer 4

in a longitudinal wave the oscillations of the particles are parallel to the direction in which the wave travels.

Question 5

what is the definition of a transverse wave ?

Answer 5

in a transverse wave the oscillations of the particles are perpendicular to the direction in which the wave travels.

Question 6

give some examples of a longitudinal wave ?

Answer 6

sound

Question 7

give some examples of a transverse waves ?

Answer 7

radio waves
microwaves
water waves
mexican wave

Question 8

what is the definition of frequency ?

Answer 8

frequency is the number of waves that pass a point each second.

Question 9

what is the definition of periodic time ?

Answer 9

the periodic time is the time taken for 1 whole oscillation.

Question 10

what is the wave speed equation ?

Answer 10

wave speed = frequency x wavelength.
(m/s) (Hz) (m)

Question 11

what is the definition of diffraction ?

Answer 11

diffraction is the way that waves spread out as they come through a narrow gap or go around obstacles.

Question 12

when does diffraction occur ?

Answer 12

diffraction occurs when waves pass through gaps.

Question 13

when does diffraction work best ?

Answer 13

diffraction works best if the wavelength of the gap is longer or narrower.

Question 14

key fact about diffraction

Answer 14

if the gap is too large most of energy gets through , but most of waves pass straight through so diffraction is ineffective.

Question 15

how can we hear around corners but not see around corners ?

Answer 15

light has a much smaller wavelength than the width of the doorway so there is little diffraction. the wavelength of sound is closer to the width of the doorway so there is more diffraction.

Question 16

describe how a longitudinal wave travels through air ?

Answer 16

the particles oscillate parallel to the direction in which the wave moves, through a series of rarefactions and compressions in the air .

Question 17

what is the definition of displacement ?

Answer 17

displacement is the distance from the equilibrium position.

Question 18

what is the definition for amplitude of a wave ?

Answer 18

the amplitude of a wave is the height of the wave form the middle to a peak or trough.

Question 19

what is constructive interference ?

Answer 19

constructive interference is when the crests or troughs of 2 waves coincide , they combine to create an amplified wave . the two waves are in phase with each other , there is 0 phase difference between them.

Question 20

what is destructive interference ?

Answer 20

destructive interference is where the crests of 1 wave are aligned with the troughs of another, they cancel each other out . the waves are out of phase or interphase with each other.

Question 21

what is the definition of superposition

Answer 21

superposition is the adding together of wave displacements that occurs when two separate sources overlap. the displacements add mathematically.

Question 22

what is phase difference ?

Answer 22

phase difference is when 2 points which are always moving in the same direction are said to be in phase.2 points a whole wavelength apart are in phase.

Question 23

what is antiphase

Answer 23

two points which are always moving in the opposite direction are said to be in antiphase. two points half a wavelength apart are in antiphase.

Question 24

describe what is meant by
coherence

Answer 24

waves are coherent of they have the same frequency and wavelength and a constant phase relationship.

Question 25

what is diffraction Grating ?

Answer 25

a diffraction grating has many lines close together.

Question 26

key facts about diffraction grating

Answer 26

the gaps in the grating are close to the wavelength of light. the rays of light will diffract when they go through the gaps.

Question 27

describe and explain what is produced when monochromatic light is shone on a diffraction grating ?

Answer 27

we would see a series of bright spots with dark areas in between. monochromatic light contains only 1 wavelength .when lights passes through slits in the diffraction grating it spreads out. the light waves overlap and interfere. at points where 1 wave has travelled a whole number of wavelengths further than the wave next to it they interfere constructively and we get a maximum. at points where 1 wave has travelled half a wavelength further than the wave next to it they interfere destructively and we get a minimum.

Question 28

definition of progressive waves ?

Answer 28

progressive waves are when waves travel, transferring energy from one position to another.

Question 29

definition of stationary waves ?

Answer 29

stationary waves are made from 2 coherent waves travelling in opposite directions.

Question 30

definition of a node

Answer 30

a node is a point that always has zero amplitude , caused by destructive interference.

Question 31

definition of an antinode ?

Answer 31

an antinode is a point of maximum amplitude , caused by constructive interference - half way between two nodes.

Question 32

how do musical instruments work ?

Answer 32

musical instruments work by producing resonance.

Question 33

what is the definition of Resonance

Answer 33

resonance is the storing of energy in a stationary wave.

Question 34

how is the mass per length calculated ?

Answer 34

mass per unit length = mass / length

Question 35

give 3 ways in which the note produced by a guitar can be altered ?

Answer 35

putting pressure on the string
plucking the string
palm muting.

Question 36

key fact about wind instruments

Answer 36

wind instruments work by creating a standing wave inside the cylinder of the instrument . they are resonators.

Question 37

Compare the types of wave formed on a guitar string and formed in a recorder when musical notes are produced.

Answer 37

Both made by vibrations​ . Both use resonance​ . Both form standing waves​. In the guitar a string vibrates, in the recorder air vibrates.​ In the guitar string there’s a transverse wave, in the recorder there’s a longitudinal wave.​ Guitar sting has nodes at both ends, recorder has antinodes and each end​ The pitch of the note from a guitar string can be changed by changing the length, thickness or tension in the string. The pitch of the note from a recorder can be changed by changing the length of the pipe.

Question 38

key fact about standing waves in an aerial

Answer 38

TV antenna’s have a reflector at the back which bounces incoming waves back and creates a stationary wave pattern. The detectors are places at the antinode positions.

Question 39

key fact about standing waves in microwaves.

Answer 39

Stationary wave patterns are caused by reflections of microwaves off the metal walls of the oven. Hot spots are occur in the antinodes and the cold spots occur in the nodes. This is why the turntable rotates.

Question 40

key fact about string theory

Answer 40

Electrons behave like stationary waves as they bounce around in each energy level. The energy levels electrons occupy represent a stationary wave pattern. Patterns with high numbers of nodes represent a higher energy level.

Question 41

what is the order of the electromagnetic spectrum ?

Answer 41

radio waves , microwaves , infra red radiation , visible light , ultraviolet light , x rays , gamma rays

Question 42

what 2 waves of the electromagnetic spectrum have the longest wavelength but the lowest frequency

Answer 42

Radio waves and microwaves.

Question 43

what 2 waves of the electromagnetic spectrum have the shortest wavelength but the highest frequency

Answer 43

x - rays and gamma rays.