0.3 Transverse pulses  (Page 3/6)

Destructive interference

Destructive interference is when two pulses meet, resulting in a smaller pulse.

The two pulses shown below approach each other at $1\mathrm{m}·\mathrm{s}{}^{-1}$ . Draw what the waveform would look like after $1\mathrm{s}$ , $2\mathrm{s}$ and $5\mathrm{s}$ .

1. After $1\mathrm{s}$

   After $1\mathrm{s}$ , pulse A has moved $1\mathrm{m}$ to the right and pulse B has moved $1\mathrm{m}$ to the left.

   

2. After $2\mathrm{s}$

   After $1\mathrm{s}$ more, pulse A has moved $1\mathrm{m}$ to the right and pulse B has moved $1\mathrm{m}$ to the left.

   

3. After $5\mathrm{s}$

   After $5\mathrm{s}$ , pulse A has moved $5\mathrm{m}$ to the right and pulse B has moved $5\mathrm{m}$ to the left.

   

Experiment: constructive and destructive interference

Aim

Apparatus

Method

1. Set up the ripple tank
2. Produce a single pulse and observe what happens
3. Produce two pulses simultaneously and observe what happens
4. Produce two pulses at slightly different times and observe what happens

Results and conclusion

Problems involving superposition of pulses

1. For the following pulse, draw the resulting wave forms after $1\mathrm{s}$ , $2\mathrm{s}$ , $3\mathrm{s}$ , $4\mathrm{s}$ and $5\mathrm{s}$ . Each pulse is travelling at $1\mathrm{m}·\mathrm{s}{}^{-1}$ . Each block represents $1\mathrm{m}$ . The pulses are shown as thick black lines and the undisplaced medium as dashed lines.

   

2. For the following pulse, draw the resulting wave forms after $1\mathrm{s}$ , $2\mathrm{s}$ , $3\mathrm{s}$ , $4\mathrm{s}$ and $5\mathrm{s}$ . Each pulse is travelling at $1\mathrm{m}·\mathrm{s}{}^{-1}$ . Each block represents $1\mathrm{m}$ . The pulses are shown as thick black lines and the undisplaced medium as dashed lines.

   

3. For the following pulse, draw the resulting wave forms after $1\mathrm{s}$ , $2\mathrm{s}$ , $3\mathrm{s}$ , $4\mathrm{s}$ and $5\mathrm{s}$ . Each pulse is travelling at $1\mathrm{m}·\mathrm{s}{}^{-1}$ . Each block represents $1\mathrm{m}$ . The pulses are shown as thick black lines and the undisplaced medium as dashed lines.

   

4. For the following pulse, draw the resulting wave forms after $1\mathrm{s}$ , $2\mathrm{s}$ , $3\mathrm{s}$ , $4\mathrm{s}$ and $5\mathrm{s}$ . Each pulse is travelling at $1\mathrm{m}·\mathrm{s}{}^{-1}$ . Each block represents $1\mathrm{m}$ . The pulses are shown as thick black lines and the undisplaced medium as dashed lines.

   

5. For the following pulse, draw the resulting wave forms after $1\mathrm{s}$ , $2\mathrm{s}$ , $3\mathrm{s}$ , $4\mathrm{s}$ and $5\mathrm{s}$ . Each pulse is travelling at $1\mathrm{m}·\mathrm{s}{}^{-1}$ . Each block represents $1\mathrm{m}$ . The pulses are shown as thick black lines and the undisplaced medium as dashed lines.

   

6. For the following pulse, draw the resulting wave forms after $1\mathrm{s}$ , $2\mathrm{s}$ , $3\mathrm{s}$ , $4\mathrm{s}$ and $5\mathrm{s}$ . Each pulse is travelling at $1\mathrm{m}·\mathrm{s}{}^{-1}$ . Each block represents $1\mathrm{m}$ . The pulses are shown as thick black lines and the undisplaced medium as dashed lines.

   

7. What is superposition of waves?
   
8. What is constructive interference?
   
9. What is destructive interference?