Interference and Diffraction

Question 1

what does the energy of a wave depend on?

Answer 1

its frequency and amplitude

Question 2

do longer or shorter wavelengths diffract more?

Answer 2

longer

Question 3

when does the most diffraction occur?

Answer 3

when the gap and the wavelength are a similar size

Question 4

what does it mean if two waves are coherent?

Answer 4

they have the same speed, frequency, wavelength and have a constant phases relationship.

Question 5

what is constructive interference?

Answer 5

when two sets of waves meet in phase (matching crests and troughs)
two crests meet to produce a larger crest

Question 6

what is destructive interference?

Answer 6

two sets of waves meet out of phase (180 degrees)

a crest and a trough combine to cancel each other out and produce no wave (only if amplitudes are equal)

Question 7

real life example of destructive interference

Answer 7

noise cancelling headphones

Question 8

what are areas of constructive interference called?

Answer 8

maximum

Question 9

what are areas of destructive interference called?

Answer 9

minimum

Question 10

what is the path difference at the central-zeroth order maximum

Answer 10

zero

Question 11

what is the path difference in areas of constructive interference

Answer 11

zero or a whole number

Question 12

what is the path difference in areas of destructive interference

Answer 12

an odd number of half wavelengths (1/2,3/2,5/2 etc.)

Question 13

equation for path difference at maximum

Answer 13

S2P-S1p=m lambda

Question 14

equation for path difference at minimum

Answer 14

S2P-S1P= (m+1/2) lambda

Question 15

what does m tell you?

Answer 15

how many wavelengths one wave travels more than the other

Question 16

equation to work out separation of slits

Answer 16

d=1/N where N is the number of lines per metre