Isaac Physics D5.7

Two microwave emitters are placed facing each other about a metre apart and coherently emit microwaves of the same frequency. A detector moved back and forth between them detects regions of maximum intensity spaced 4.0cm apart. Calculate the frequency of the microwaves.

I tried f = v/4L, f =V/lambda and using speed of sound in air : 330m/s

Still couldn't get the answer, help

Reply 1

Stonebridge

13

It's not sound we are dealing with here, it's microwaves.
These travel at the 'speed of light'.

Regarding the calculation:
The antinodes (places of maximum intensity) in a standing wave are one half wavelength apart.
So the 4cm represents this half wavelength.
Convert it to metres.
Try again and report back if you succeed or not. :smile:

Reply 2

Rlornie13

OP

2

Original post by Stonebridge

It's not sound we are dealing with here, it's microwaves.
These travel at the 'speed of light'.

Regarding the calculation:
The antinodes (places of maximum intensity) in a standing wave are one half wavelength apart.
So the 4cm represents this half wavelength.
Convert it to metres.
Try again and report back if you succeed or not. :smile:

Would i be using f = v/4L?

Reply 3

Stonebridge

13

Original post by Rlornie13

Would i be using f = v/4L?

Not quite.
To find f, yes, you use the wave equation v=fλ which gives f = v / λ
But the 4cm in this case represents half the wavelength.
So the wavelength is 8cm. Convert to metres.
Use whatever value for the speed of light is given either in the question on on your data sheet.

Reply 4

Lhacking

4

Hi I know this is from a while ago but I have the same Q and just can’t figure it out... I did f=3x10^8/0.08 but it’s not correct.. I need a bit of help please

Reply 5

lolacash

2

Original post by Lhacking

Hi I know this is from a while ago but I have the same Q and just can’t figure it out... I did f=3x10^8/0.08 but it’s not correct.. I need a bit of help please