Diffraction and Interference

Question 1

What is Diffraction?

Answer 1

Diffraction is the bending of waves as they pass the edge of an obstacle or through aperture(A gap in a barrier).

Question 2

How much do they diffract?

Answer 2

The amount of diffraction that occurs depends on the wavelength of the wave and the width of the object or aperture. Waves with relatively low wavelengths (high frequencies) diffract very little; waves with approximately equal or relatively high wavelengths (low frequencies) diffract significantly.

Question 3

Wavelength - Diffraction

Answer 3

Through the concept of width doesn’t apply to the corner of an obstacle, the wavelength still affects the amount of diffraction.

This explains why sound waves can bend around some obstacles , humans can hear sounds up to 17m. However light waves can generally not as the longest visible wavelength of light is 700nm.

Question 4

Applications:

Answer 4

Since high frequency sounds (shorter wavelengths) are diffracted less, their direction relative to the listener can be pinpointed more easily.

Ultrasound frequencies (frequencies greater than 20 kHz) are used for sonar and medical imaging for this reason. They are
also used by bats, dolphins, and
other animals for echolocation.

Question 5

Superposition Principle

Answer 5

Formation of complex sounds. It is possible for two waves to occupy the same region of space/a medium at the same time. Two waves with varying frequency and amplitude in the same region will create a complex wave with varying amplitude.

Question 6

Interference:

Answer 6

Interference is a result of superposition. Two waves can either reinforce each other, resulting in a wave of higher amplitude (constructive interference), or counteract each other, resulting in a wave of lower amplitude (destructive interference).

With transverse waves, the two waves can push particles in the same direction (constructive) or opposite directions (destructive).

In longitudinal two waves can compress the same parts of the medium(constructive) or compress each others rarefactions (destructive).

Question 7

Resonance

Answer 7

All objects that can oscillate tend to do so at a specific frequency known as their natural frequency or resonant frequency.

Resonance is when an object is exposed to vibrations at a frequency equal to their natural frequency. The vibration in one object causes the vibration in another to become strong. If the amplitude is to high it will destroy the object.