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5.2 Waves and wavelengths

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By the end of this section, you will be able to:
  • Describe important physical features of wave forms
  • Show how physical properties of light waves are associated with perceptual experience
  • Show how physical properties of sound waves are associated with perceptual experience

Visual and auditory stimuli both occur in the form of waves. Although the two stimuli are very different in terms of composition, wave forms share similar characteristics that are especially important to our visual and auditory perceptions. In this section, we describe the physical properties of the waves as well as the perceptual experiences associated with them.

Amplitude and wavelength

Two physical characteristics of a wave are amplitude and wavelength ( [link] ). The amplitude    of a wave is the height of a wave as measured from the highest point on the wave ( peak    or crest ) to the lowest point on the wave ( trough    ). Wavelength refers to the length of a wave from one peak to the next.

A diagram illustrates the basic parts of a wave. Moving from left to right, the wavelength line begins above a straight horizontal line and falls and rises equally above and below that line. One of the areas where the wavelength line reaches its highest point is labeled “Peak.” A horizontal bracket, labeled “Wavelength,” extends from this area to the next peak. One of the areas where the wavelength reaches its lowest point is labeled “Trough.” A vertical bracket, labeled “Amplitude,” extends from a “Peak” to a “Trough.”
The amplitude or height of a wave is measured from the peak to the trough. The wavelength is measured from peak to peak.

Wavelength is directly related to the frequency of a given wave form. Frequency refers to the number of waves that pass a given point in a given time period and is often expressed in terms of hertz (Hz)    , or cycles per second. Longer wavelengths will have lower frequencies, and shorter wavelengths will have higher frequencies ( [link] ).

Stacked vertically are 5 waves of different colors and wavelengths. The top wave is red with a long wavelengths, which indicate a low frequency. Moving downward, the color of each wave is different: orange, yellow, green, and blue. Also moving downward, the wavelengths become shorter as the frequencies increase.
This figure illustrates waves of differing wavelengths/frequencies. At the top of the figure, the red wave has a long wavelength/short frequency. Moving from top to bottom, the wavelengths decrease and frequencies increase.

Light waves

The visible spectrum    is the portion of the larger electromagnetic spectrum    that we can see. As [link] shows, the electromagnetic spectrum encompasses all of the electromagnetic radiation that occurs in our environment and includes gamma rays, x-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves. The visible spectrum in humans is associated with wavelengths that range from 380 to 740 nm—a very small distance, since a nanometer (nm) is one billionth of a meter. Other species can detect other portions of the electromagnetic spectrum. For instance, honeybees can see light in the ultraviolet range (Wakakuwa, Stavenga,&Arikawa, 2007), and some snakes can detect infrared radiation in addition to more traditional visual light cues (Chen, Deng, Brauth, Ding,&Tang, 2012; Hartline, Kass,&Loop, 1978).

This illustration shows the wavelength, frequency, and size of objects across the electromagnetic spectrum.. At the top, various wavelengths are given in sequence from small to large, with a parallel illustration of a wave with increasing frequency. These are the provided wavelengths, measured in meters: “Gamma ray 10 to the negative twelfth power,” “x-ray 10 to the negative tenth power,” ultraviolet 10 to the negative eighth power,” “visible .5 times 10 to the negative sixth power,” “infrared 10 to the negative fifth power,” microwave 10 to the negative second power,” and “radio 10 cubed.”Another section is labeled “About the size of” and lists from left to right: “Atomic nuclei,” “Atoms,” “Molecules,” “Protozoans,” “Pinpoints,” “Honeybees,” “Humans,” and “Buildings” with an illustration of each . At the bottom is a line labeled “Frequency” with the following measurements in hertz: 10 to the powers of 20, 18, 16, 15, 12, 8, and 4. From left to right the line changes in color from purple to red with the remaining colors of the visible spectrum in between.
Light that is visible to humans makes up only a small portion of the electromagnetic spectrum.

In humans, light wavelength is associated with perception of color ( [link] ). Within the visible spectrum, our experience of red is associated with longer wavelengths, greens are intermediate, and blues and violets are shorter in wavelength. (An easy way to remember this is the mnemonic ROYGBIV: r ed, o range, y ellow, g reen, b lue, i ndigo, v iolet.) The amplitude of light waves is associated with our experience of brightness or intensity of color, with larger amplitudes appearing brighter.

Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
Eunice Reply
what is a capacitor?
Raymond Reply
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
Saheed Reply
50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
Haryormhidey Reply
how many start and codon
Esrael Reply
what is field
Felix Reply
physics, biology and chemistry this is my Field
ALIYU
field is a region of space under the influence of some physical properties
Collete
what is ogarnic chemistry
WISDOM Reply
determine the slope giving that 3y+ 2x-14=0
WISDOM
Another formula for Acceleration
Belty Reply
a=v/t. a=f/m a
IHUMA
innocent
Adah
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
Nassze Reply
how do lnternal energy measures
Esrael
Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
JALLAH Reply
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
Destiny Reply
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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Source:  OpenStax, Psychology. OpenStax CNX. Feb 03, 2015 Download for free at https://legacy.cnx.org/content/col11629/1.5
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