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Chapter 38: Q 10 (page 1114)

An FM radio station broadcasts with a power of 10 kW at a frequency of 101 MHz.

a. How many photons does the antenna emit each second?

b. Should the broadcast be treated as an electromagnetic wave or discrete photons? Explain.

Short Answer

Expert verified

a) No. of photons are 1.49脳1029.

b) The broadcast will be treated as an electromagnetic wave.

Step by step solution

01

Step 1. Given Information is :Power = 10 kWFrequency = 101 Mhz 

We need to find out :

a) No. of photons emitted by antenna each second.

b) Whether the broadcast be treated as an electromagnetic wave or discrete photons.

02

Step 2. Part a) Using the expression of energy of the photon.

E0=hfAnd,鈭�E=P鈭�tHence,thenumberofphotonswillbeequaltototalenergydividedbytheenergyofonephoton.N=鈭�EE0N=P鈭�thfN=10脳103W1s6.63脳10-34101脳106HzN=1.49脳1029

03

Step 3. Part b) Using the concepts of Electromagnetic waves and Discrete Photons.

The broadcasts includes a huge no. of photons and it is of the order 1029.

As a result, we won't be able to quantify or notice the energy transfer, despite the fact that it is inherently discrete. It will appear to us as if the energy is continuously transmitted, hence we should approach this problem using electromagnetic wave formalism.

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