In the electromagnetic spectrum, which of the following types of electromagnetic radiation listed here has the longest wavelength and therefore the lowest frequency?

Introduction / Context:
The electromagnetic spectrum contains many different types of radiation, from very long wavelength radio waves to very short wavelength gamma rays. As wavelength increases, frequency decreases, and as wavelength decreases, frequency increases. This question focuses on four parts of the spectrum infrared, visible, ultraviolet and gamma radiation and asks you to identify which has the longest wavelength among them.

Given Data / Assumptions:

• The options are infrared, gamma, ultraviolet and visible radiation.
• All are parts of the electromagnetic spectrum and travel at the same speed in vacuum.
• Wavelength and frequency are inversely related for electromagnetic waves.
• We are comparing typical wavelength ranges for each region.

Concept / Approach:
In order of increasing frequency (and decreasing wavelength), key parts of the electromagnetic spectrum are arranged roughly as: radio waves, microwaves, infrared, visible, ultraviolet, X rays and gamma rays. This means infrared radiation lies just below visible light in frequency and has longer wavelengths than visible light. Ultraviolet radiation lies above visible light in frequency and therefore has shorter wavelengths. Gamma rays are at the extreme high frequency end of the spectrum and have the shortest wavelengths of all. Thus, among the four given options, infrared radiation has the longest wavelength.

Step-by-Step Solution:
Step 1: Recall the general order of the electromagnetic spectrum from long wavelength to short wavelength.Step 2: Place the given options in this order: infrared, visible, ultraviolet, gamma.Step 3: Recognise that infrared has wavelengths slightly longer than red light in the visible spectrum.Step 4: Recognise that ultraviolet has wavelengths shorter than violet light in the visible spectrum.Step 5: Remember that gamma radiation has extremely short wavelengths and very high frequencies.Step 6: Conclude that infrared radiation has the longest wavelength among the listed options.

Verification / Alternative check:
Typical wavelength ranges can be used as a quick check. Infrared wavelengths are roughly from 700 nanometres to 1 millimetre. Visible light spans about 400 to 700 nanometres. Ultraviolet radiation ranges from about 10 to 400 nanometres. Gamma rays have wavelengths shorter than about 0.01 nanometres. Comparing these ranges clearly shows that infrared wavelengths are longest, visible are shorter, ultraviolet are even shorter and gamma rays are the shortest among the given choices.

Why Other Options Are Wrong:
Gamma radiation has the shortest wavelengths and highest frequencies in the entire electromagnetic spectrum, so it cannot have the longest wavelength. Ultraviolet radiation has shorter wavelengths than visible light and therefore also cannot be the answer. Visible radiation lies between infrared and ultraviolet; its wavelengths are longer than ultraviolet but shorter than infrared. Only infrared radiation has the longest wavelengths among the listed types.

Common Pitfalls:
Students sometimes confuse energy, frequency and wavelength and may assume visible light must be largest because it is most familiar. Others incorrectly place ultraviolet below visible and infrared above visible in the spectrum. To avoid these errors, memorise the correct order: radio, microwave, infrared, visible, ultraviolet, X ray, gamma, moving from long wavelength to short wavelength.

Final Answer:
Infrared radiation has the longest wavelength among the listed types of electromagnetic radiation.