HESI A2 Exam: Light
• What is the speed of light?
• What is the number of cycles of a wave that pass a specific point in 1 second?
• As a wave's wavelength ________ the frequency ____________.
• Visible light falls in which range in the electromagnetic spectrum?
• Which type of wave has the shortest wavelength and is also the most dangerous in the electromagnetic spectrum?
Intro
In a vacuum, the speed of light is 3.00 x 10^8 m/s.
Photons carry energy, and the amount of energy a photon carries is directly proportional to its frequency and inversely proportional to its wavelength.
Frequency is the number of cycles of a wave that pass a specific point in 1 second.
Waves
Microwaves can be used to broadcast information through space. They are good for transmitting information because the energy can go through substances such as clouds and light rain.
Radio waves have the lowest energy levels and are transmitted by radio broadcasts, TV broadcasts, and cell phones.
A transverse wave has movement of the particles at right angles (perpendicular) to the motion of the energy. Movement of a wave through a solid object like a stretched rope or a trampoline is an example of this type of wave.
A longitudinal wave involves movement of the particles parallel to the motion of the energy. Sound waves moving through the air are an example of this type of wave.
A mechanical wave is a wave that is an oscillation of matter, and therefore transfers energy through a medium.
Wavelength
A wavelength is the distance between two successive peaks of a wave.
As a wave’s wavelength increases, the frequency decreases, and as wave’s wavelength decreases, the frequency increases.
Wavelength is also measured in meters (m) - it is a length after all. The frequency, f, of a wave is the number of waves passing a point in a certain time. We normally use a time of one second, so this gives frequency the unit hertz (Hz), since one hertz is equal to one wave per second.
Electromagnetic Spectrum
The common designations are radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma-rays. Visible light falls in the range of the EM spectrum between infrared (IR) and ultraviolet (UV).
Gamma rays are the most energetic and dangerous form of electromagnetic waves. Gamma rays are a type of harmful radiation. Typical size: 0.000001 nanometers (the width of an atomic nucleus). Gamma rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum.
Electromagnetic radiation is energy that is transferred through free space or through a medium in the form of electromagnetic waves, such as radio waves, visible light, and gamma rays.
A particle of electromagnetic radiation is known as a photon and sometimes called a light quantum.
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