11.4 Diffraction and polarisation

Question 1

What is diffraction?

Answer 1

Diffraction is the spreading out of a wave as it passes through an aperture (a small gap) or when they encounter an obstacle.
Wave speed/length and frequency are unaffected.
Diffraction can only occur when the size of the aperture is similar to the wavelength.

Question 2

What is the difference between refraction and diffraction?

Answer 2

Refraction is the bending of waves when they pass from one medium to another with different optical properties, while diffraction is the bending or spreading of waves around obstacles or through small openings. Refraction involves changes in direction and wave speed, while diffraction is related to interference and the wavelength-dependent behavior of waves.

Question 3

What condition ensures that diffraction is increased?

Answer 3

For the best amount of diffraction, the size of the aperture must be close to or similar in length to the wavelength of the wave. The larger the aperture is, the less diffraction that will occur.

Question 4

What is polarisation?

Answer 4

Polarisation means that the particles oscillate along one
direction only, which means that the wave is confined to
a single plane.
Unpolarised light - light which oscillates in many different planes.
Polarised light - light which oscillates in one plane only

Question 5

What type of wave can polarisation occur only in?

Answer 5

Polarization can occur in transverse waves but not in longitudinal waves. This is because in transverse waves, the oscillations are perpendicular to the direction of energy transfer, but in longitudinal waves, the oscillations are parallel to the direction of energy transfer. In summary, in transverse, it is moving in multiple planes; in longitudinal, it is already moving in one plane only.