Question

Q2.

a) Explain what is meant by diffraction of waves, and give two examples of when diffraction is useful.

b) A loudspeaker has a diameter of 0.15 m. Using the principle of circular hole diffraction, calculate the angle at which the first minimum occurs when a. Sound of frequency 3400 Hz ( = 0.10 m) is emitted. b. Sound of frequency 10 kHz ( = 0.034 m) is emitted.

c) Use these answers to give one reason why woofers (speakers with a larger diameter used for lower frequencies) and tweeters (speakers with smaller diameters used for higher frequencies) are used in speaker cabinets to improve sound quality.

d) Give another reason why different diameter speakers are used for different frequencies.

Answer 1

a) generally the path of a wave changes due to three phenomena namely reflection,refraction,diffraction

the process involving the change in path of the wave it passes through a small opening is known as diffraction

examples of diffraction are

1) oceam waves diffract around the onstacles

2) sound waves can diffract around objects,which is why one can still hear some one calling even when hiding

behind a tree

b) given diameter if the hole = d = 0.15m

we have formula

as per the given information in both cases n =1

case a)

  

= 41.8 degrees

case b)

  

  

= 13.1 degrees

c) always a range of diffracting angle is preferrable for greater focus

from the above calculation we observe as frequency increase (wave length decrease) the angle diffracting decreases

so speakers with large diameter are used for lower frequencies and speakers with small diameter are used for high frequencies

d) damping is the other reason for using different diametres for differenr frequencies

thankyou