Electromagnetic Spectrum Overview

Electromagnetic Spectrum

• The electromagnetic spectrum (EM spectrum) encompasses all types of electromagnetic radiation.
• It consists of seven regions, ordered by frequency, wavelength, or energy.
• Wavelength (λ) is the distance between wave crests, measured in meters (m).
• Frequency (f) is the number of waves passing a point per second, measured in Hertz (Hz) or s⁻¹.
• All EM radiation travels at the speed of light (3 × 10⁸ m/s).
• Frequency and wavelength are inversely proportional: higher frequency, shorter wavelength.
• Energy and frequency are directly proportional: higher energy, higher frequency.
• Radio waves have the lowest energy, longest wavelengths.
• Gamma rays have the highest energy, shortest wavelengths.
• Visible light is a small portion of the EM spectrum.

Continuous Spectrum

• The visible light spectrum appears as white light but contains different colors.
• The continuous spectrum shows all wavelengths within a specific range.
• In the visible spectrum, red light has the lowest energy and violet has the highest.

Emission Line Spectra

• Emission line spectra are unique to each element.
• They are formed when energy is applied to a gas sample like hydrogen, then viewed through a spectroscope.
• The pattern of lines represents specific wavelengths or frequencies.
• A continuous spectrum shows all wavelengths, while a line spectrum displays only specific wavelengths as colored lines on a dark background.
• The lines in a line spectrum converge at higher energies (shorter wavelengths).
• Studying these line spectra allows us to identify elements.

Electron Energy Levels and Transitions

• Electrons occupy energy levels or shells around the nucleus (Bohr model).
• Energy levels are quantized.
• Closer energy levels (ground state) mean lower energy, while farther ones (excited state) mean higher energy.
• Electron transitions:
  • Electrons can absorb energy, moving to higher energy levels and become excited.
  • Electrons release specific energies (as photons), transitioning to lower energy levels, forming visible light.
• The amount of energy released or absorbed correlates to a specific wavelength of light, leading to a distinctive line in the emission spectrum.
• Transitions between different energy levels determine the specific wavelengths of characteristic light.
  • Transitions from higher energy levels to lower levels generate higher energy light.