Hint: If we know the frequency, then from the relation between frequency and wavelength. We can find out the waves having the highest wavelength.
Complete step by step answer:
In the magnetic spectrum we are having the range of wavelengths and also the range of the frequencies of the different waves like gamma rays, x-rays, ultraviolet, visible rays, radar waves, microwaves, television waves and radio waves and further this visible rays consists or comprises of the seven colors they are: violet, indigo, blue, green, yellow, orange and red which are also differ in their frequencies and hence the wavelength of the colors also changes accordingly.
These different waves have decreased in frequency in the same order as mentioned above. Since we already know that the frequency is inversely proportional to the wavelength and hence the wavelength will increase in the same order that means radio waves are having the highest wavelength. And in the visible range red is having the highest wavelength due to having the least frequency in the VIBGYOR.
So from the given above options radio waves are having the highest wavelength due to having the least frequency.
So, the correct answer is “Option B”.
Note: We know that the relation between the frequency and wavelength is inversely proportional or the wavelength is inversely proportional to the frequency. That is
Where $\lambda $ is the wavelength
$C$ Is the speed of light