Understanding Light Spectra
Overview
This lecture explains what a spectrum is and how analyzing the spectrum of light from an object can reveal information about the object, using graphs and physical principles.
What Is a Spectrum?
- A spectrum is the pattern of light an object emits, showing the intensity of every wavelength.
- It is commonly displayed as a graph with wavelength (λ, lambda) on the x-axis and intensity (brightness) on the y-axis.
- Longer wavelengths (e.g., radio waves) are on the right; shorter wavelengths (e.g., gamma rays) are on the left.
- The spectrum of an object shows how bright each wavelength is, indicating how much of each type of light is being emitted.
Interpreting the Spectrum Graph
- A tall graph section means the object is emitting a lot of that wavelength of light.
- Objects can emit many types of wavelengths, but the amount varies.
- A perfect light source produces a single smooth, hill-shaped spectrum, emitting at least a little of every wavelength.
How Spectra Are Obtained
- Light from an object is split into its component wavelengths using a prism or similar device, through a process called refraction.
- This splitting creates a rainbow effect (visible spectrum) or equivalent for invisible wavelengths, showing the pattern of colors/wavelengths present in the light.
- If some wavelengths are missing, gaps appear in the rainbow or graph.
Types of Spectra
- A continuous spectrum is smooth and contains all wavelengths (ideal case).
- Perfect light sources produce continuous spectra, but natural objects rarely (if ever) do.
- Real objects usually show missing or altered sections in their spectra compared to the continuous ideal.
Key Terms & Definitions
- Spectrum — The pattern of light intensity at different wavelengths emitted by an object.
- Wavelength (λ, lambda) — The distance between peaks of a wave; determines type of light (radio, visible, gamma, etc.).
- Intensity — The brightness or strength of light at a particular wavelength.
- Refraction — The bending of light as it passes through substances like a prism, used to split light into its component wavelengths.
- Continuous Spectrum — A smooth distribution of all wavelengths with no gaps; produced by perfect light sources.
Action Items / Next Steps
- Review the three main things a spectrum can tell us, to be covered in the upcoming lessons.
- Be prepared for further discussion on the types of spectra found in nature and what they reveal about objects.