Superposition

Question 1

What is the principle of superposition?

Answer 1

When two waves meet, the resultant displacement is the vector sum of the displacements due to each individual wave.

Question 2

What does it mean for sources to be coherent?

Answer 2

Sources are said to be coherent if they have constant phase difference. It is only achievable when the two sources have the same frequency, wavelength and wave speed.

Question 3

What is a stationary wave?

Answer 3

They are waves in which there is no transfer of energy.

Question 4

Conditions for stationary waves to form.

Answer 4

1. opposite direction
2. same frequency and speed
3. same amplitude
4. coherent and polarised

Question 5

What is Diffraction?

Answer 5

Diffraction is the spreading of waves when they pass through an aperture or around an obstacle.

Question 6

What is a constructive interference?

Answer 6

It is when two waves meet in phase at a point, they reinforce each other and the resultant amplitude of the wave is a maximum.

Question 7

What is a destructive interference?

Answer 7

It is when two waves meet in anti phase at a point, they cancel each other and the resultant amplitude of the wave is a minimum.

Question 8

What is the Rayleigh’s Criterion?

Answer 8

Rayleigh’s Criterion states that two sources are just resolved if the central maximum of one diffraction patterns falls on the first minimum of the diffraction pattern of the other.

Question 9

Characteristic of diffraction grating.

Answer 9

As the number of slits increases, each maxima becomes narrower. As the number of slits increases, intensity of maxima increases.

Question 10

Characteristic of single slit diffraction

Answer 10

One central fringe that is largest. It will have different colours at the edge of the maximas.

Question 11

Characteristic of double slit diffraction

Answer 11

Alternating bright and dar fringes.