2.4 Superposition and Interference of Waves

Question 1

Diffraction

Answer 1

spreading out of waves as they pass around an obstacle or go through a gap

Question 2

when does max diffraction occur?

Answer 2

wavelength of wave equal to size of gap

Question 3

principle of superposition

Answer 3

resultant displacement when two or more waves meet at a point is the vector sum of the displacements of the individual waves at that point

Question 4

constructive interference

Answer 4

waves superimpose resulting in a wave of larger amplitude

Question 5

destructive interference

Answer 5

waves superimpose resulting in a wave of smaller amplitude

Question 6

interference pattern

Answer 6

pattern showing some areas where there is constructive interference and a large wave disturbance (maxima), and other areas where there is destructive interference and little or no wave disturbance (minima)

Question 7

what has to happen for an observable interference pattern?

Answer 7

same type of wave
coherent sources - same wavelength + frequency so constant phase difference
comparable amplitudes

Question 8

complete destructive interference

Answer 8

2 waves with equal amplitudes, meet 180o out of phase, will be total destructive interference and waves will cancel each other out

Question 9

conditions required to produce standing wave

Answer 9

2 progressive waves of sample amplitude, frequency and speed
travelling through same medium in opposite directions meet
interfere with each other
must be same type of wave

Question 10

energy transfer of stationary waves

Answer 10

no transfer of energy along medium

Question 11

how can stationary waves be set up on stretched string?

Answer 11

set up by fixing ends of string using vibration generator to create wave that travels down string and reflects

Question 12

resonant frequencies

Answer 12

string vibrates with large amplitude
resonance occurs
standing wave set up

Question 13

1st mode equations

Answer 13

L = wavelength/2
wavelength = 2L

Question 14

2nd mode equations

Answer 14

L=wavelength

Question 15

3rd mode equations

Answer 15

L=3wavelength/2
wavelength = 2L/3

Question 16

4th mode equations

Answer 16

L=2wavelength
wavelength = L/2

Question 17

in standing waves in air columns, what is at the closed end?

Answer 17

node

Question 18

in standing waves in air columns, what is at the open end?

Answer 18

antinode

Question 19

what does young’s double slit experiment prove?

Answer 19

light is a wave

Question 20

constructive and destructive interference in young’s double slit

Answer 20

constructive - bright areas
destructive - dark areas

Question 21

light source in young’s double slit experiment

Answer 21

monochromatic

Question 22

monochromatic

Answer 22

consists of light of only one wavelength

Question 23

what is the observation in young’s double slit experiment?

Answer 23

series of bright and dark equally spaced fringes

Question 24

equation for young’s double slit

Answer 24

wavelength = ay/d

Question 25

how to get an accurate value for fringe separation

Answer 25

separation of number of fringes should be measured and length divided by number of fringes

Question 26

diffraction grating

Answer 26

made by making many parallel scratches on surface of flat piece of transparent material

Question 27

scratches on diffraction grating

Answer 27

opaque but areas between scratches can transmit light

Question 28

similarity between diffraction grating and young’s double slit

Answer 28

bright fringes on dark background

Question 29

difference between diffraction grating and young’s double slit

Answer 29

far fewer fringes and gaps between them are larger in diffraction grating

Question 30

equation for diffraction grating

Answer 30

dsino=nwavelength

Question 31

how is the highest order of maxima visible calculated by

Answer 31

n=d/wavelength