Question

Which type of electromagnetic radiation has the longest wavelength? (a) visible (b) ultraviolet (c) infrared (d) X-ray

Short answer

Infrared (c) has the longest wavelength.

Step-by-step solution

Identify the Types of Electromagnetic Radiation

Begin by listing the different types of electromagnetic radiation given in the options: visible, ultraviolet (UV), infrared (IR), and X-ray.

Understand the Electromagnetic Spectrum

Recognize that the electromagnetic spectrum is organized by frequency and wavelength. Generally, as the frequency increases, the wavelength decreases. The spectrum is arranged from longest wavelength to shortest as follows: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Determine the Longest Wavelength

Based on the order provided in the electromagnetic spectrum, infrared (IR) radiation has a longer wavelength than visible, ultraviolet, and X-ray radiation.

Key concepts

Wavelength and Frequency

When exploring the fascinating world of the electromagnetic spectrum, it's crucial to understand the relationship between wavelength and frequency. Simply put, wavelength is the distance between successive peaks of a wave, typically measured in meters. In contrast, frequency is the number of waves that pass a point in one second, measured in hertz (Hz). Interestingly, there's a tight-knit relationship between these two: as the frequency of a wave increases, its wavelength decreases, and this inverse relationship is encapsulated in the formula:
\[ c = \lambda \times f \]
where \( c \) is the speed of light, \( \lambda \) (lambda) represents the wavelength, and \( f \) is the frequency. This formula is vital as it unifies the concept of the electromagnetic spectrum. It allows us to calculate one property if we know the other, along with the speed of light which is a constant (approximately \( 3 \times 10^8 \) meters per second).
Let's consider light waves as an example. If a particular type of light has a high frequency, it will have a short wavelength, such as ultraviolet light. Conversely, radio waves have lower frequencies, which corresponds with their longer wavelengths.

Electromagnetic Radiation Types

The electromagnetic spectrum encompasses all types of electromagnetic radiation, which vary in their wavelength and frequency. Understanding the different types is key for comprehending the diverse range of electromagnetic behaviors and applications.
Here's a quick rundown of the main types, in order of increasing frequency and decreasing wavelength:

• Radio Waves: Used in communications, they have the longest wavelengths and lowest frequencies.
• Microwaves: Employed in radar and cooking food, they possess slightly higher frequencies than radio waves.
• Infrared (IR): Emitting from warm objects, infrared waves are what you feel as heat and have shorter wavelengths than microwaves.
• Visible Light: The only part of the spectrum we can see, it forms the rainbow of colors from red to violet.
• Ultraviolet (UV): These are the waves that cause sunburn and are just beyond the violet end of visible light.
• X-Rays: High-energy radiation that can penetrate most materials; commonly used in medical imaging.
• Gamma Rays: Produced by nuclear reactions, they have the shortest wavelengths and are the most energetic form of electromagnetic waves.

Each type of radiation has its unique set of properties and uses, which depends on its place within the spectrum. These variations allow us to harness electromagnetic waves for a myriad of purposes, ranging from medical diagnostics to telecommunications.

Properties of Electromagnetic Waves

Electromagnetic waves possess fundamental properties that allow us to use them in diverse ways. One quintessential feature is that they all travel at the speed of light in a vacuum, which equates to approximately \( 3 \times 10^8 \) meters per second. Despite their speed, these waves exhibit different behaviors based on their wavelengths and frequencies.
Some key properties to highlight include:

• Transverse Waves: Electromagnetic waves are transverse, which means their oscillations are perpendicular to the direction of wave travel.
• Energy Levels: Each wave carries energy, with those of higher frequencies (like X-rays and gamma rays) carrying more energy than lower frequencies (like radio waves).
• No Medium Required: Unlike sound waves, electromagnetic waves do not need a medium to travel through; they can pass through the vacuum of space.
• Polarization: Due to their transverse nature, these waves can be polarized, which involves restricting the wave's vibrations to a single plane.

The properties of electromagnetic waves are fundamental to understanding their interactions with matter and how they're utilized in technology. Advanced applications like wireless communications and medical imaging diagnostic tools heavily rely on these properties. Furthermore, the photoelectric effect—where light can cause certain materials to emit electrons—alluding to the dual particle-like and wave-like nature of light, is foundationally built on understanding these wave properties.