12.1 - 12.6

Question 1

what’s the principle of superposition of waves

Answer 1

when two waves meet at a point the resultant displacement equals the sum of the individual displacements

Question 2

what is constructive interference

Answer 2

superposition of two waves in phase. the resultant wave has a greater amplitude than the individual waves

Question 3

what is destructive interference

Answer 3

superposition of two waves in antiphase. the resultant wave has a smaller amplitude than the original waves

Question 4

define coherence

Answer 4

two waves/wave source that are coherent have a constant phase difference

Question 5

define ‘path difference’

Answer 5

the difference in the distance travelled by two waves from the source to a specific point

Question 6

whats the path difference for constructive and destructive interference

Answer 6

constructive: xλ
destructive: xλ+ (1/2)λ
where x is an integer

Question 7

how does Young’s double-slit experiment work?

Answer 7

he used one source of monochromatic light. by directing it through a single slit the light diffracted and arrived at the double slit in phase. it then diffracts again at the double slit. each slit acts as a coherent source. this causes an interference pattern.

Question 8

what does Young’s double-slit experiment prove?

Answer 8

it demonstrates the wave nature of light

Question 9

what is a stationary wave

Answer 9

when two waves of the same frequency travel in opposite directions and are superimposed. there is no transfer of energy

Question 10

whats a node

Answer 10

a point on a stationary wave where there is destructive interference. the displacement is always 0

Question 11

whats an antinode

Answer 11

a point on a stationary wave where there is constructive interference. the displacement is the greatest (at the amplitude)

Question 12

what’s the distance between adjacent nodes or antinodes

Answer 12

half the wavelength of the stationary wave

Question 13

how is phase difference different along a stationary wave?

Answer 13

between adjacent nodes, the phase difference is always 0 because each point reaches its maximum positive displacement at the same time.

on the other side of the nodes, the points are in antiphase. as one reaches its maximum positive displacement the other reaches its maximum negative

Question 14

how are stationary waves on a string formed

Answer 14

when plucked a progressive wave travels along the string. It reflects off each end creating two progressive waves traveling in opposite directions forming a stationary wave

Question 15

what is the fundamental frequency

Answer 15

the minimum frequency of a stationary wave.

Question 16

whats the fundamental frequency of a string

Answer 16

when the wavelength is twice the length of the string

Question 17

what is a harmonic

Answer 17

an integer multiple of the fundamental frequency. these are the frequencies that can form stationary waves

Question 18

how are stationary waves different in a tube open at one end and closed at the other

Answer 18

a node must be at the closed end but an antinode must be at the open end for a stationary wave to form. the fundamental frequency is 1/4 λ

Question 19

how are harmonics different in a tube open at one end and closed at the other

Answer 19

they are not integer multiples of the fundamental frequency. they are odd number multiples. this is because there must be a node at one end and an antinode at the other.