3B.4 wave interference

Question 1

What is wave interference?

Answer 1

The superposition of two or more waves producing a resultant wave pattern.

Question 2

What are coherent waves?

Answer 2

Waves that have the same frequency and a constant phase difference.

Question 3

What is path difference?

Answer 3

The difference in distance travelled by two waves from their sources to a point.

Question 4

Give an example of two-source interference.

Answer 4

Two loudspeakers producing sound or Young’s double-slit experiment with light.

Question 5

What are fringes in light interference?

Answer 5

The alternating bright and dark bands on a screen produced by interference.

Question 6

What is the condition for constructive interference?

Answer 6

Path difference = nλ, where n = 0,1,2,3…, producing a bright fringe.

Question 7

What phase difference produces constructive interference?

Answer 7

2nπ radians (0°, 360°, 720° …).

Question 8

What is the condition for destructive interference?

Answer 8

Path difference = (2n+1)λ/2, producing a dark fringe.

Question 9

What phase difference produces destructive interference?

Answer 9

(2n+1)π radians (180°, 540° …).

Question 10

What is the central maximum in interference?

Answer 10

The bright fringe at the centre where the path difference is 0.

Question 11

Why does interference occur in a double-slit experiment?

Answer 11

The slits act as two coherent sources of waves.

Question 12

What is the relationship between path difference and phase difference?

Answer 12

One wavelength corresponds to a phase difference of 2π radians.

Question 13

How can interference be demonstrated in a ripple tank?

Answer 13

Two point sources produce overlapping circular waves forming nodal and antinodal lines.

Question 14

What two formulas must be remembered for interference?

Answer 14

Constructive: path difference = nλ. Destructive: path difference = (2n+1)λ/2.