Electromagnetic waves are categorized according to their frequency f or, equivalently, according to their wavelength λ = c/f. Visible light has a wavelength range from ~400 nm to ~700 nm. Violet light has a wavelength of ~400 nm, and a frequency of ~7.5*1014 Hz. Red light has a wavelength of ~700 nm, and a frequency of ~4.3*1014 Hz. Show Visible light makes up just a small part of the full electromagnetic spectrum. Electromagnetic waves with shorter wavelengths and higher frequencies include ultraviolet light, X-rays, and gamma rays. Electromagnetic waves with longer wavelengths and lower frequencies include infrared light, microwaves, and radio and television waves.
Problem:Two microwave frequencies are authorized for use in microwave ovens, 900 and 2560 MHz. Calculate the wavelength of each. Solution:
Problem:Distances in space are often quoted in units of light years, the distance light travels in one year. Solution:
Spectroscopy:What can we learn by analyzing the EM spectrum emitted by a source? The velocities of particles with thermal energy are changing almost all the time. The particles are accelerating. Accelerating charged particles produce electromagnetic radiation. The power radiated is proportional to the square of the acceleration. Higher rates of velocity change result in higher frequency (shorter wavelength) radiation. The observed intensity of thermal radiation emitted by as a function of wavelength can be described by the Planck Radiation Law (Physics 221). When light passes through or reflects or scatters of matter, it interacts with the atoms and molecules. Atoms and molecules have characteristic resonance frequencies. The preferentially interact with light waves of exactly those frequencies. When excited in collisions, atoms and molecules emit light with a set of characteristic frequencies. This results in a line spectrum. Only light with a discrete set of wavelengths is produced and the spectrum is not continuous, but consist of a set of emission lines. That set characterizes the atoms and molecules which produced it and can be used to identify those atoms and molecules and their environment. When light with a continuous distribution of wavelengths passes through a low-density material, the atoms and molecules of the material absorb light waves with the same set of characteristic frequencies that appear in their emission spectrum. This produces an absorption spectrum, a nearly continuous spectrum with missing lines. The
absorption spectrum can also be used to identify those atoms and molecules and their environment. Embedded Question 3Please explore this simple simulations of various molecules interacting with electromagnetic radiation of different wavelength. Discuss this with your fellow students in the discussion forum! What is different about the different parts of the electromagnetic spectrum?The different types of radiation are defined by the the amount of energy found in the photons. Radio waves have photons with low energies, microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and, the most energetic of all, gamma-rays.
What is different about the different parts of the electromagnetic spectrum quizlet?EM waves differ in frequency, wavelength and energy level. + High frequency waves have short wavelength and HIGH energy. + Low frequency waves have long wavelengths and low energy. Electromagnetic waves differ in frequency (and wavelength).
Why do different parts of the electromagnetic spectrum have different properties?Since radiations from all parts of the spectrum travel at the same speed, and the frequencies vary, the wavelengths of the different parts of the electromagnetic spectrum must also be different. The differences in wavelength can be huge.
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