You are Here: Home >< Physics

# Exam Question on Waves (Stuck) - Depth OCR Watch

1. Question: Why can't BBC Radio 1 be broadcast on 98.9 FM over the whole country, using a large number of local transmitters all tuned to the same frequency?

(Hint - think about superposition, and constructive and destructive interference).

This was a sample question given by my teacher.

I thought that different waves from different transmitters would out of of phase from one - another so the waves would interfere destructively in certain regions so the resultant waves are smaller, and in certain regions where the phase different is 180º, this would mean that a shadow would be created where no one can tune into the radio station.

Is this right?
2. That seems good, but the last bit is not completely right. For example if there are 3 waves coming to a point and lets call them A, B and C. If A=1m, B=2m and C=-3m, then at that point the A+B+C=0, the waves A,B,C aren't in phase, but they aren't in antiphase either. So it might better to say, some regions the waves will cancel out completely leaving a "shadow", as you mentioned.

Also, if this was an exam question and worth more than a couple marks, I would add another line describing the superposition principle. E.g. When two or more waves superimpose at a point the resultant displacement is the sum of the individual waves.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 8, 2016
Today on TSR

### Last-minute PS help

100s of personal statements examples here

### More pressure for kinky sex?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.