Two microwave signals of nearly equal wavelengths can gener- ate a beat frequency if both are directed onto the same microwave detector. In an experiment, the beat frequency is 100 MHz. One microwave generator is set to emit microwaves with a wavelength of 1.250 cm. If the second generator emits the longer wavelength, what is that wavelength

the longer wavelength is 1.2552 cm

Explanation:

given that

beat frequency = 100 MHz = 100 × 10⁶ Hz

λ₁ = 1.250 cm = 0.0125 m

we know that beat frequency of two simultaneous frequencies f₁ and f₂ is expressed as;

 = | f₁ - f₂ |

we know that microwave travels at a speed of light, so for any electromagnetic wave traveling at speed of light c with wavelength λ; frequency is;

f = c / λ

hence our beat frequency becomes

= c ( 1/λ₁ - 1/λ₂)

to find the longer wavelength,  λ₂

= c ( 1/λ₁ - 1/λ₂)

divide both side by c

/c =  ( 1/λ₁ - 1/λ₂)

1/λ₂ = 1/λ₁ - /c

λ₂ =  [1/λ₁ - /c ]⁻¹

so we substitute in our values

we know that speed of light c = 3 × 10⁸

so

λ₂ =  [ (1/0.0125) - (100 × 10⁶ /3 × 10⁸) ]⁻¹

λ₂ =  [80 - 0.3333 ]⁻¹

λ₂ =  [79.6667 ]⁻¹

λ₂ =  0.01255 m

λ₂ =  0.012552 × 100 cm

λ₂ =  1.2552 cm

Therefore, the longer wavelength is 1.2552 cm

e) none of the above answers are correct