Of the following, the correct arrangement of electromagnetic spectrum in decreasing order of wavelength is _______.

Fill in the blank with the correct answer from the options given below

The correct answer is Radio waves, microwaves, Infrared waves, visible waves, X-rays.

To understand why this is the correct order, let us look at the electromagnetic spectrum. The electromagnetic spectrum is the range of all types of electromagnetic radiation, organized by wavelength or frequency.

Wavelength ($\lambda$) and frequency ($f$) are inversely proportional to each other, related by the speed of light ($c$) through the formula:
$c=f\cdot \lambda$
Therefore, electromagnetic waves with the longest wavelengths have the lowest frequencies, and those with the shortest wavelengths have the highest frequencies.

Let us list the components of the electromagnetic spectrum in decreasing order of wavelength (from the longest wavelength to the shortest wavelength):
1. Radio waves (wavelengths ranging from meters to kilometers)
2. Microwaves (wavelengths ranging from millimeters to centimeters)
3. Infrared waves (wavelengths ranging from about 700 nanometers to 1 millimeter)
4. Visible light/waves (wavelengths ranging from about 400 nanometers to 700 nanometers)
5. Ultraviolet waves (wavelengths ranging from about 10 nanometers to 400 nanometers)
6. X-rays (wavelengths ranging from about 0.01 nanometers to 10 nanometers)
7. Gamma rays (wavelengths less than 0.01 nanometers)

By comparing the options with this sequence, we can see that:
${\lambda }_{\text{Radio waves}}>{\lambda }_{\text{microwaves}}>{\lambda }_{\text{Infrared waves}}>{\lambda }_{\text{visible waves}}>{\lambda }_{\text{X-rays}}$
This perfectly matches the third option.