Question

Some copper compounds emit green light when they are heated in a flame. How would you determine whether the light is of one wavelength or a mixture of two or more wavelengths?

Short answer

Use a prism or diffraction grating and spectroscope to observe and measure the light's spectrum.

Step-by-step solution

Understanding the Problem

We need to determine if the emitted green light from heated copper compounds is a single wavelength or contains multiple wavelengths. This involves analyzing the light spectrum.

Use of Prism or Diffraction Grating

To separate the light into its component wavelengths, pass it through a prism or a diffraction grating. This will disperse the light based on wavelength.

Observing the Dispersed Light

After dispersion, observe the resulting spectrum. A pure single wavelength will produce a single line of color, while multiple wavelengths will produce several lines, each corresponding to a different wavelength.

Utilization of Spectroscopy

Employ a spectroscope to measure the exact distribution of wavelengths. The spectroscope provides a visual output where separate wavelengths show distinct peaks.

Key concepts

Prism

A prism is an optical device used to separate light into its component colors or wavelengths. When light passes through a prism, it is refracted, or bent, at different angles depending on the wavelength of the light. This separation occurs because different wavelengths of light move at different speeds when they enter a new medium. The classic rainbow effect observed when light passes through a prism is due to this refracting property. By observing the light that exits a prism, one can determine if the light source is composed of multiple wavelengths. If there’s only one color band, it signifies a single wavelength. In contrast, several bands of colors indicate multiple wavelengths are present.

Diffraction Grating

A diffraction grating is another tool used to separate light into its constituent wavelengths, similar to a prism but working on a different principle. It consists of many closely spaced slits, which disperse incoming light by interference. As light waves pass through these slits, they diffract and overlap, causing them to interfere with one another. This interference pattern spreads the light into its spectrum. The extent of the separation depends on the slit spacing and the light's wavelength. Using a diffraction grating can produce a more precise separation than a prism, as it can distinguish between closely spaced wavelengths. Thus, diffraction gratings are widely used in spectrometers to analyze complex light sources.

Light Spectrum

The light spectrum refers to the range of wavelengths of light, spanning from the shortest gamma rays to the longest radio waves, visible to the human eye. When a source emits light, it may consist of one or multiple wavelengths, contributing to the complexity of its spectrum. Visible light, a small part of the spectrum, includes colors ranging from violet (shortest wavelength) to red (longest wavelength). The light spectrum is crucial in identifying the composition of light sources. By analyzing the spectrum, using either a prism or a diffraction grating, we can determine whether a light source like the copper compound emits light at a single or multiple wavelengths, contributing to our understanding of the emitted green light.

Wavelengths

Wavelength is a key characteristic of light waves, defined as the distance between successive crests of the wave. It's denoted in units like nanometers (nm) or meters (m). Different wavelengths correspond to different colors in visible light. Shorter wavelengths, such as blue or violet light, have higher energy and frequency, while longer wavelengths like red have lower energy. When analyzing light, determining the wavelengths present helps identify the nature of the light source. If multiple wavelengths are detected, it suggests a mixture of colors producing the observed light. Spectroscopic methods, utilizing tools such as prisms and diffraction gratings, are essential for examining these wavelengths accurately and determining if the green light from copper compounds consists of a single wavelength or several.