waves and the particle behaviour of light

Question 1

what is a transverse wave

Answer 1

A type of wave in which the particles oscillate at right angles to the direction the waves travel

Question 2

what is a longitudinal wave

Answer 2

a type of wave in which the particles oscillate parallel to the wave direction

Question 3

what is wavelength

Answer 3

the distance between two matching points on neighbouring waves

Question 4

what are rarefactions

Answer 4

regions in a wave where the medium is less dense compared to the surrounding areas.

Question 5

what are compressions

Answer 5

regions of increased density in a wave.

Question 6

what is period

Answer 6

the time taken for one complete oscillation

Question 7

if an oscillator has a frequency of 10Hz what will be the oscillations per second

Answer 7

10

Question 8

what is frequency

Answer 8

the number of oscillations per second

Question 9

what does monochromatic mean

Answer 9

have the same wavelength

Question 10

what is superposition

Answer 10

when two or more waves overlap in space, the resulting amplitude is equal to the sum of the individual amplitude

Question 11

what is a wave when it is in phase

Answer 11

the position within the oscillation of a wave so their troughs and crests are aligned

Question 12

what is constructive interference

Answer 12

happens when the resultant wave has a larger amplitude than any of the individual waves

Question 13

what is destructive interference

Answer 13

happens when the resultant wave has a smaller amplitude then the individual waves

Question 14

what is amplitude

Answer 14

is the maximum displacement of a particle in the wave from its equilibrium position (from equilibrium to peak or trough)

Question 15

what is antiphase

Answer 15

when the crest of one wave aligns with the trough of another

Question 16

what is wavefront

Answer 16

an imaginary surface or line that connects all the points of a wave that have the same phase

Question 17

what does coherent mean

Answer 17

so when they have constant relative phase or when they have zero or constant phase difference and the same frequency

Question 18

give two definitions of a standing wave

Answer 18

1.oscillates in time but does not move in space
2.con only be formed when a waves motion is restricted within a given finite space

Question 19

give two definitions of a progressive wave

Answer 19

1.moves continuously in a medium in the same direction
2.can be either longitudinal or transverse

Question 20

state the relationship between gap distance and wavelength

Answer 20

partial diffraction D > λ
full diffraction D = λ
no diffraction D < λ

Question 21

what is Huygens principal

Answer 21

all points of a wavefront of sound in a vacuum or transparent medium
(air) may be regarded as a new sources of wavelets what expand in every direction at a rate depending on their velocities

Question 22

what does the diffraction pattern show in Youngs double slit experiment

Answer 22

1. constructive interference between light rays form bright strips called fringes (interference fringes or maxima) on the screen
2. Destructive interference forms dark strips, also called dark fringes (or minima) on the screen

Question 23

how can we describe the fringes in the double slit experiment

Answer 23

identical and has the same width and intensity

Question 24

what does the interference pattern show

Answer 24

the regions of constructive and destructive interference (light and dark fringes)

Question 25

what is each bright fringe equal to

Answer 25

a peak of maximum intensity

Question 26

what does each dark fringe show

Answer 26

a trough of minimum or zero intensity

Question 27

what are maxima

Answer 27

formed by the constructive interference of light

Question 28

what are minima

Answer 28

formed by the destructive interference of light

Question 29

what is phase difference

Answer 29

how far apart the waves are when comparing their phases, measured in radians

Question 30

what is phase difference measured in

Answer 30

radians

Question 31

what is 1 radian

Answer 31

1 radian is equal to 57.2958Deg

Question 32

how do you calculate 1 radian

Answer 32

1Rad × 180/π and reverse for degrees

Question 33

why do we use a circle to to represent a wave

Answer 33

a circle is symmetric and starts to change in height fast near the x axis, but gets slow near the y axis

Question 34

explain diffraction grating

Answer 34

Diffraction gratings are formed by large numbers of equally spaced slits or lines that diffract the light falling on them. The path difference between two adjacent slits is the same as in the double slit case, x=dsinθ. So the condition for a maximum remains the same

Question 35

how do you calculate diffraction gratings

Answer 35

nλ = dsinθ

Question 36

what is path difference

Answer 36

The difference in distance travelled by two waves from their sources to the point where they meet

Question 37

how are path differences measured in

Answer 37

multiples of wavelengths

Question 38

what is light

Answer 38

light is the fluctuation of electromagnetic waves at right angles to electric fields

Question 39

what is another unit for photon charge instead of joules

Answer 39

electron volt

Question 40

what is the definition of the electron volt

Answer 40

equal to the kinetic energy gained by an electron when it is accelerated by a potential difference of one volt

Question 41

why do we use a electron volt

Answer 41

joules is too large of a unit

Question 42

what is the value of a electron volt

Answer 42

1.16*10^-19

Question 43

what is ionisation

Answer 43

the removal of a electron from its atomic outer shell resulting in a delocalised electron and a positive atomic ion this happens when the atom is hit by another energy source

Question 44

what is the name of the energy that the incident particle gives off

Answer 44

ionisation energy

Question 45

what are the main causes of ionisation

Answer 45

usually radiation but sometimes heat particles

Question 46

what is excitation

Answer 46

the promotion of electrons from lower to higher energy levels within an atom

Question 47

why do electrons de excite

Answer 47

exited states are usually very unstable and due to the positive attraction of the atoms nucleus the electrons are forced down into a lower energy level

Question 48

what is the bi product of de excitation

Answer 48

photons

Question 49

how can we express emitted photon energy

Answer 49

hf = E2 - E1

Question 50

what are the conditions of excitation

Answer 50

when the photon energy is exactly equal to the energy required to excite

Question 51

what is plancks constant

Answer 51

6.63*10^-34 js

Question 52

how are standing waves formed (6 marks)

Answer 52

-in a medium when two waves having equal amplitude and frequency -in opposite directions along the same line -in a confined space -formed by superposition of a forward wave and the reflective wave

Question 53

give the equation for the first harmonic

Answer 53

L = 1/2*λ

Question 54

the second harmonic equation

Answer 54

L = 2/2*λ

Question 55

the third harmonic equation

Answer 55

L = 3/2*λ

Question 56

the n'th term harmonic

Answer 56

L = n/2*λ

Question 57

how do you rearrange the harmonics equation to give lambda

Answer 57

λ = 2L

Question 58

express Snells law as a formulae

Answer 58

n=sinθ1/sinθ2

Question 59

what is the refractive index

Answer 59

ratio of the apparent speed of light in the air or vacuum to the speed in the medium

Question 60

what happens to waves when they speed up

Answer 60

wave deviates away from the normal

Question 61

what happens when the wave slows down

Answer 61

wave deviates towards the normal

Question 62

what is the angle of incidence

Answer 62

The angle at which a light ray hits a medium. Measured from a line perpendicular to the surface of the medium.

Question 63

what is the angle of refraction

Answer 63

The angle at which light rays travel after transferring into a different refractive index material. Measured from a line perpendicular to the surface of the medium.

Question 64

state what it is meant by the ground state

Answer 64

the ground state is the most stable energy level of a atom it is also the lowest energy level

Question 65

describe the process by which mercury atoms become excited in a florescent tube (3 marks)

Answer 65

When an electric current is passed through the tube, the electrons in the gas collide with the mercury atoms. This collision transfers energy to the atom, allowing the atom to excite. Shortly after the collision, the atom to de-excite. During the de-excitation process, the mercury atom emits photons in the ultraviolet.