Question

Radio Ceylon broadcast at 25 m. What is the frequency of the station?

Answer 1

Hint: Wavelength is given in the question and with the help of it we have to find the frequency of the station. We know, the speed of a radio wave is equal to the speed of light. Thus, we get the speed of the radio wave. Use the formula giving a relationship between frequency, wavelength and speed of the wave to answer this question. Substitute the values in this formula and find the frequency of the station.
Formula used:
$\lambda= \dfrac {c}{\nu}$

Complete answer:
Given: Wavelength, $\lambda= 25 m$
Speed of a radio wave is equal to the speed of light. Thus, the speed of the radio wave is given by,
$c= 3 \times {10}^{8} {m}/{s}$
We know, the relationship between frequency and wavelength is given by,
$\lambda= \dfrac {c}{\nu}$
Where, c is the speed of the wave
              $\lambda$ is the wavelength of the radiation
              $\nu$ is the frequency of the wave
Substituting values in above equation we get,
$25= \dfrac {3 \times {10}^{8}}{\nu}$
$\Rightarrow \nu= \dfrac {3 \times {10}^{8}}{25}$
$\Rightarrow \nu= 0.12 \times {10}^{8} Hz$
Hence, the frequency of the station is $0.12 \times {10}^{8} Hz$.

Note:
To solve these types of questions, students must be clear with the concept and applications of frequency of sound waves travelling for specific distances. The frequency of broadcast varies with the distance of broadcast. The broadcast frequency is much higher for shorter distances. Students must always remember that all the electromagnetic waves have the same speed which is equal to the speed of light (c).