Diffraction is the spreading of waves that occurs when waves pass through a narrow opening or around a small obstacle. When diffraction occurs, the direction and velocity of waves may change but the wavelength and frequency remain unchanged. The amplitude of diffracted waves is smaller than the incident waves as the wave energy spreads out over a larger surface area. Diffraction is more pronounced for waves passing through narrow openings or around small obstacles when the size of the opening or obstacle is smaller than the wavelength of the waves. Diffraction has various applications in everyday life such as in harbors where sea walls use diffraction of ocean waves to protect boats.

1. PHYSICS
1.4 Diffraction of Waves
Prepared by:
Qhaiyum
Budi
Nadzri
Aimran
Abdullah Azam

2. Definition of Diffraction
Diffraction is the spreading of waves that happens when it passes
through a narrow opening or when it passes round a small obstacle along
it’s path.

3. Characteristics of Diffraction
When diffraction occurs:
i. Wave direction changes.
ii. Wave velocity, ν, changes.
iii. Wavelength, λ, is unchanged.
iv. Frequency, ƒ, is unchanged.
v. Speed unchanged.
The amplitude, а, of the diffracted wave is
smaller compared to that of the incident wave, as
the wave energy is spread out over a larger
surface.

4. Diffraction of Water Waves
Waves are diffracted more if the
i. Opening is narrow.
ii. Obstacle is small.

5. When the width of the opening is smaller than the wavelength, λ,
the wave will be well diffracted.
When the opening is very
narrow, the wave is very well
diffracted.
The size of the opening is too
big, the wave is not well
diffracted.

6. When the size of the obstacle is smaller than the wavelength, λ,
the wave will be well diffracted.
The size of the obstacle is small,
the waves are well diffracted.
The size of the obstacle is too big,
the waves are not well
diffracted.

7. Diffraction of Light Waves
Light is diffracted when it passes through a very narrow opening such as
a pin-hole or a slit.
The diffraction pattern produced by light consists of a central bright fringe
and a few smaller bright fringes, separated by dark fringes.

8. Diffraction of Sound Waves
Sound can be diffracted as it passes through window slits or wall
corners.
The cleaner standing at the point where he
cannot see the radio but he can hear the
sound from it due to diffraction of sound
waves by the wall corner.

9. Applications in Everyday Life
Sea-walls in a harbour jetty:
i. Strong concrete walls are usually
built in the sea near a harbour jetty
to protect the boats from damage
caused by strong waves.
ii. When strong waves rush towards the
harbour jetty, the concrete barriers
reflect some of the waves and
allow others to diffract through the
opening between the barriers.

10. That’s All
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