What is Wavelength: Definition and 1000 Discussions

In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ).
The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths.Wavelength depends on the medium (for example, vacuum, air, or water) that a wave travels through. Examples of waves are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary.
The range of wavelengths or frequencies for wave phenomena is called a spectrum. The name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum.

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  1. S

    Is speed of em waves directly proportional to magntiude of wavelength

    I read that speed is directly proportional to wavelength in a medium. so does it mean that gamma is the slowest in air compared to the rest of the waves?
  2. Y

    What is the light's wavelength?

    Homework Statement A diffraction grating having 500 lines/mm diffracts visible light at 30°. What is the light's wavelength? d = 1/500(lines/mm) = 2x10-6(m) θ = 30° = pi/6 rad⇔ Homework Equations d*sin(θm) = mλ The Attempt at a Solution when i rearranged the equation, i got λ =...
  3. M

    Using e = hc/λ to find wavelength of light emitted

    Homework Statement Hello there, a question that I have been given is to "find the wavelenght of light emitted from an electron jumping from the 2nd to the 6th orbital (or vise versa if that matters). The atom is hydrogen" Homework Equations E= \frac{hc}{λ} The Attempt at a Solution...
  4. D

    Compton scattering problem - how much did wavelength change by?

    Homework Statement How much will the wavelength of the incident X-ray photon change by if it is scattered by 30 degrees when it interacts with an electron? Homework Equations This is Compton scattering. This is the equation I used: lambda ' - lambda (0) = (h)/(m(e)c) (1-cos...
  5. nukeman

    Quick question: Finding the wavelength?

    Quick question: Finding the wavelength?? Homework Statement The energy of a photon is 5.87 x 10^-20 J. What is its wavelength in nanometers? I use E = H(c/λ) Correct? Since I am trying to find λ, I change it to this? λ = H(c/E) ? 6.63x10^-34 x (3 x 10^8 / 5,87 x 10^-20) =...
  6. L

    Doppler Shift and photons with a wavelength of one Plank length

    If this is the wrong place to be posting this, feel free to lock this thread. I wasn't sure if this belonged in "classical physics" or "quantum physics"; this seemed like the appropriate place, but I'm not 100% certain, as it does involve subatomic particles. Anyways, to get to the matter at...
  7. aleemudasir

    Wavelength of matter waves at speed equal to zero.

    According to de-broglie's equation λ=h/p, so a/c to this equation what would be wavelength of particle at zero speed?
  8. D

    Light of 500nm wavelength is reflected

    Homework Statement Hi:redface: Light of 500nm wavelength is reflected from a thin film of air between two glass plates. The thickness of the film is 1000mn. a) How much farther does the light reflected from bottom surface travels than the light reflected from the top of the film...
  9. M

    Relationship between wavelength and voltage?

    Hi all, I am in introductory physics and we are doing a self-designed lab. For my lab, I wanted to study the relationship between the wavelength of light and voltage. To do this, measured how much voltage drop there was in a single celled solar panel when I put colored filters over a light that...
  10. M

    De Broglie Wavelength: Should Electron Have Same Rest Energy?

    While deriving De-Broglie wavelength we equate mc^2 to hf and then for electron we change c to v but as far I know mc^2 is rest energy then how could c be converted into v for electron.Shouldnt it have the same rest energy?
  11. H

    Depth of pit of CD - why 1/4 of wavelength?

    Homework Statement Why does the depth of the pit have to be 1/4 of the wavelength? Homework Equations I understand that this causes two beams to interfere destructively because the path difference resulted is 1/2 of a wavelength - however, I cannot prove this geometrically - can somebody...
  12. B

    Wavelength and resonant length equation

    What's the relationship between a wavelength and the difference between consecutive resonant lengths (ΔL) for closed air columns? Basically, what's an equation for λ in terms of Δresonant length? Thanks!
  13. A

    Two source interference determining wavelength

    Homework Statement A laser with wavelength d/8 is shining light on a double slit with slit separation 0.300 . This results in an interference pattern on a screen a distance L away from the slits. We wish to shine a second laser, with a different wavelength, through the same slits. What is the...
  14. E

    Finding the wavelength from the work function in photoemission

    Homework Statement a) Write down the formula that relates the maximum electron energy, Emax. to the frequency of the incident light in the photoelectric effect. b) Calculate the maximum wavelength of light for which photoemission occurs for light incident on a metal whose workfunction...
  15. 5

    Relationship between wavelength and refraction

    While playing around with some laser diodes I have at home ~(405, 550, 650 nm) I have noticed that the refracted angles through some mediums (all?) is different. That is, if I fire my 405nm laser through some water at \theta_{1}=80°, the angle of refraction is ~\theta_{2}=47.01±0.05°. Now...
  16. S

    Calculate De Broglie Wavelength of Electron | Help for Final Exam

    I'm reviewing for one of my final exam and I can't seem to figure out this problem: Find the Debroglie wavelength of an electron with a KE of 40 ev. I got an answer of 3.9 x 10^-10 m. I keep getting it wrong and I'm not sure what to do. Thanks in advance!
  17. R

    Index of refraction related to wavelength & frequency

    I'm going through the Light & Optics chapter of Kaplan MCAT prep material & am having a hard time conceptually understanding the relationship between index of refraction & wavelength or with frequency. It says in the book that n = c/v, & "when the speed of the light wave varies with...
  18. B

    Is cycle the same as wavelength?

    Is cycle the same as wavelength? Thanks!
  19. S

    Calculating Maximum Kinetic Energy of Ejected Electrons After Wavelength Doubles

    Homework Statement Photons of energy 12 eV are incident on a metal. It is found that current flows from the metal until a stopping potential of 8.0 V is applied. If the wavelength of the incident photons is doubled, what is the maximum kinetic energy of the ejected electrons? Homework...
  20. S

    Wavelength used in interference

    Homework Statement Two flat glass plates are stacked and a thin paper strip is inserted between them at one side, creating a narrow wedge-shaped space between the plates. As shown in the figure below, monochromatic light that has a wavelength in air is directed at the plates from above. When...
  21. nukeman

    How to find the wavelength of a Photon with no mass?

    Homework Statement Hey guys, So I just did a problem here: (its find wavelength of particle with mass) https://www.physicsforums.com/showthread.php?t=596936 But I need to figure out how to find the wavelength of a Photon with no mass. I know the formula I need is this: wavelength =...
  22. nukeman

    How to find the wavelength of a particle with mass?

    Homework Statement Does the following question ask what my title says? I study pack says "How to find the wavelength of a particle with mass?" So, is the following question good? Question: What is the deBroglie wavelength of an electrion with a speed of 2.2x10^6 m/s Answer I got...
  23. J

    Bose-Einstein Condensation & de Broglie wavelength

    Homework Statement Bose-Einstein condensation of a fluid occurs when the de Broglie wavelength of a "typical" particle becomes greater than the average nearest-neighbor distance. One can interpret the momentum in the de Broglie equation as p=\sqrt{<p^{2}>} where <p^{2}> means the thermal...
  24. I

    How Do You Calculate the Wavelength of Colliding Waves?

    Homework Statement Two sinusoidal waves with equal wavelengths travel along a string in opposite directions at 7.72 m/s. The time between two successive instants when the antinodes are at a maximum height is 0.324 s. What is the wavelength (in m)? Homework Equations vt=x Also...
  25. edpell

    DeBroglie Wavelength: Proton at Room Temp Scattering Behavior

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  26. M

    Standing waves, frequency, wavelength and speed D; Help

    What is the wavelength of the interfering waves? Homework Statement Standing waves are produced in a string by sources at each end with a frequency of 10.0 Hz. The distance between the third node and the sixth node is 54 cm. a) What is the wavelength of the interfering waves? b) What is...
  27. N

    Basic physics/ wavelength and displacement questions

    Hi guys, i'd really like to understand physics but for some reason I'm not coping. Not sure if it's the calculations or something. But I'm willing to learn, I'd appreciate some help with this problem:Homework Statement A B string on a guitar with a length of 33cm is held fixed at both ends...
  28. M

    Calculating the wavelength of a laser? (Diffraction grating)

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  29. N

    Wavelength vs. Frequency Modulation

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  30. M

    Is this the Wavelength? (Diffraction)

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  31. T

    Rentgen tube, De-Broile wavelength and Compton effect

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  32. T

    Find wavelength of a quantum of electromagnetic radiation

    Homework Statement A quantum of electromagnetic radiation has an energy of 0.877 keV. What is its wavelength? The speed of light is 2.99792 × 10 8 m/s, and Planck’s constant is 6.62607 × 10−34J · s. Answer in units of nm Homework Equations E=hf v=fλ ... λ=v/(E/h) The Attempt...
  33. R

    Stationary electron broglie wavelength

    de broglie's formulation: λ=h/(mv) the more the momentum of a particle, the less wave-like behaviour it shows. But what if we have electron which is stationary, i.e. zero speed, according to formula λ becomes ∞. What does this mean? Does the electron disappear?
  34. B

    What is the Energy Ratio of Two Photons with Different Wavelengths?

    Homework Statement Suppose one photon has a wavelength of 6770 nanometers while a second photon has a wavelength 1/6 as large. What is the ratio of the energy of the second photon divided by the first photon? Homework Equations Not sure. The Attempt at a Solution Don't...
  35. 9

    What Is the Wavelength of the Earth According to De Broglie's Equation?

    So I was reading about De Broglie's theory of particle-wave duality the other day and I came across the equation: λ=h/p. I expect most of you are familiar with this equation but if you're not, it is: wavelength = Planck's length over momentum (mass x velocity). So I thought i'd try and find...
  36. P

    How many wavelengths of sound are between the two animals?

    Homework Statement A rhinoceros is calling to her mate using sound wave whose frequency is 5.0 Hz. Her mate is 480 m away. The air is 35°C. How many wavelengths of the sound are between the two animals? Homework Equations v = 331 + (.6)*T v = wavelength*frequency The Attempt at a...
  37. R

    Why is Diffraction dependent upon wavelength?

    I've searched online and on the forum but still can't find an explanation or mechanism behind why diffraction is dependent upon wavelength. For example, assume a water wave that diffracts around a small boat (smaller than the wavelength). The degree of diffraction decreases as the boat gets...
  38. C

    Wavelength Change and Refractive index in a Conductor

    Homework Statement Hey guys, new to the forums so hopefully you can help. I have been given the frequency (and hence the wavelength) of a microwave of 10GHz, and the conductivity of Al which is 3.53x10^7 Siemens/m. From this I have worked out the skin depth. But it asks also what the...
  39. A

    Bending of waves around obstacles and the effect of wavelength

    why does the wavelength of light or sound waves affect the degree of bending?I know the mathematical formula for fringe width,but i want to know the physical reasons behind the phenomenon of bending. Taking the example of light passing through a small slit,the huygens principle talks about...
  40. J

    Slit width order of wavelength

    In diffraction why the slit width has to be the order of wavelength of wave? I don't understand. The smaller the width of the slit i think the more effective diffraction becomes. Why the width has to be order of the wavelength?
  41. H

    Same frequency different wavelength?

    how can waves like sound have different wavelengths with same frequency?(Wα1/frequency) For eg, in air vel=wav*freq which in solid is more. So, either frequency or wavelength should change. But, since frequency is source dependent, its only the wavelength that changes. My Doubt is that how...
  42. M

    Why Wavelength of Light Changes in Refraction

    When light or any other electromagnetic wave enters from one medium to another, there is a change in its speed. Speed of a wave is given as v = frequency x wavelength. My question is, what does change, frequency, wavelength or both? If you say... this change in speed is generally attributed...
  43. J

    Wavelength, energy and photons.

    This follows some questions/points made in my light and sight thread. I have been trying to work out the relationship/difference between photons and waves. I now think that a photon is a discrete particle like amount of energy needed to jump an electron from one orbit to another, perhaps call...
  44. S

    Why does long wavelength mean more energy OR less energy

    When looking at say water waves, long wavelength means high energy e.g. a tsunami, and waves in a rough sea - compared say to ripples on a pond. But when looking at photons and electrons and other "matter waves", short wavelength equals high energy. Why is it completely the opposite?
  45. A

    Relationship between wavelength of light and size of hole it can go through?

    Doing some reading into photonics and nanophotonics. It seems that if a hole is smaller than the wavelength of light, then the light cannot go through the hole. For example, if a hole is smaller than 570nm (green), then green light and light with wavelengths less than 570nm can pass through...
  46. H

    What happens to wavelength of sound in liquid?

    We know that speed of sound in liquid is more than in air. Also, velocity of sound = wavelength X frequency. Now there's a change in speed of sound from air to liquid, so, wavelength or frequency should have got changed... But, generally, frequency won't change for an object (correct me...
  47. X

    Do gamma and X-ray wavelength photons also exist as collapse able wave fx's?

    This question has gone unanswered by our friends in nuclear/atomic threads. My question relates to a solitary Tc^99m decay in particular, and to gamma rays in general. If light is a collapse able wave function, are different wavelength energies the same, ie gamma, x, radio, etc. My...
  48. C

    What is the Uncertainty in Wavelength for an Excited Atomic State?

    Homework Statement An excited atomic state has a lifetime of 1 ms. What is the uncertainty in its energy? The photon emitted during its decay is 550 nm in wavelength. What is the uncertainty and fractional uncertainty in its wavelength? Homework Equations ΔEΔt≥hbar/2 The...
  49. S

    Infrared Wavelength: Same Emission for All Materials?

    Do different materials (i.e. granite, steel, water, etc.), all at the same temperature, emit the same infrared wavelength?
  50. vhbelvadi

    How does the number of photons determine wavelength?

    While reading on Cerenkov radiations I've been coming across statement to this effect: It has been noted that the number of photons at a particular frequency or wavelength, as it turns out, is proportional to 1/l2 How is that (mathematically) so?
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