Interference

Question 1

Principle of Superposition

Answer 1

When two similar types of waves meet at a point, the sum of their individual displacements is equal to the displacement of the resultant wave (Positive or Negative)

Question 2

Superposition Explanation

Answer 2

When two waves of the same type arrive in the same place, they pass through each other
The two wave pass beyond the point of intersection, they separate out again and continue unaffected

Question 3

Path Difference

Answer 3

The difference in distance between two different sources and a detector

Question 4

Interference

Answer 4

Superposition of two progressive waves from coherent sources to produce a resultant wave with displacement equal to the sum of the individual wave’s displacements

Question 5

Coherence

Answer 5

Two waves are emitted with a constant phase difference, same frequency, polarised in the same plane and similar amplitude
If the two waves are coherent, then their superposition resembles another wave of the same frequency

Question 6

Constructive Interference

Answer 6

When two coherent waves meet, they interfere
If they are exactly in phase, the amplitudes add up

Question 7

Destructive Interference

Answer 7

If the waves (same amplitude) are exactly out of phase, the amplitudes cancel out

Question 8

Youngs Double Split Experiment

Answer 8

Use a single source of Monochromatic light (Laser) and split it into two waves using a double slit
Monochromatic - Light with a single wavelength / frequency
As the waves diffract, when they collide, they interfere, creating fringes of dark and light on the screen

Question 9

Interference Patterns

Answer 9

Depends on Path or Phase Difference
If a maximum is detected (bright fringe for visible light) it shows constructive interference:
Phase difference of 0 / 360
Path difference of nλ (n is an integer)
If a minimum is detected (dark fringe for visible light ) it shows destructive interference:
Phase difference of 0 / 360
Path difference of (2n + 1) / 2λ

Question 10

Double Slit with White Light

Answer 10

Proves the wavelength of light and the wave properties of light
Each spectrum is one fringe or maximum
Central fringe is white as a path difference for all wavelengths is 0
The next maximum is a spectrum as the path difference is different

Question 11

Interference Equation

Answer 11

λ = ax/D
λ: Wavelength (m)
a: Slit / Source Separation (m)
x: Fringe Separation (m)
D: Distance between slits and screen (m)
a &laquo_space;D
Any two source interference (Sources must be coherent)

Question 12

Interference of Sound Waves

Answer 12

Used to Find λ
Using two loudspeakers and a microphone and CRO
Coherent Sources
Maxima (Loud), Minima (Quiet)

Question 13

Interference of Microwaves

Answer 13

Used to Find λ
Two microwave transmitters and a detector (or a metal sheet with a double slit)
Coherent Sources