Wave Speed Relation

The fundamental wave relation from NCERT Class 11, Chapter 15 (Waves) links speed, frequency and wavelength as $v=f\lambda$, so the wavelength is $\lambda =v/f$. For radio waves the speed is that of light, $v=3\times 10^8$ m/s, and the frequency is $f=100$ MHz $=100\times 10^6=10^8$ Hz. Dividing, $\lambda =\frac{3\times 10^8}{10^8}=3$ m. The option 30 m would result from using 10 MHz instead of 100 MHz. The option 0.3 m arises from a factor-of-ten slip in the exponent, using $10^9$ Hz. The option 300 m corresponds to a 1 MHz AM-band frequency, not the given FM value. A plausibility check: FM radio around 100 MHz is well known to have wavelengths of a few metres, and the units work out since dividing metres per second by inverse seconds leaves metres, confirming both magnitude and dimensions of the answer.