What is Wavelengths: Definition and 231 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. R

    A Can someone explain this statement on luminous transmittance?

    I have a table of wavelengths and percentage values. Can someone explain this statement: "The following pages give percentage luminous transmittance at wavelengths 500 to 700 nm. for the standard Illuminant "C" adopted by the CIE." What I need is the ratio of the energy coming out of the...
  2. S

    Are cones in eyes sized to the light's wavelengths they perceive?

    Each of the 3 primary colors have a different wavelength so I'm wondering if that means each type of cone has a different size than another type.
  3. DaveC426913

    B Can sunglasses fully protect against UV sensitivity?

    Is there a 1:1 correlation between the wavelengths that a given pair of quality sunglasses blocks and the wavelength that trigger the photochemical change? For example: if I know my wife I am particularly sensitive to UVB light, and my wife's my sunglasses only darken under UVA light, then I...
  4. J

    Wavelength / signal which would pass through concrete and rubble

    Greetings, Please imagine a huge pile of rubble, meters deep. Somewhere inside, there's a device emitting a certain signal. This signal can be picked up by a radar-like device which locates the origin of that signal, with the least interference from the pile of rubble, concrete blocks, metals...
  5. C

    Speed of sound from resonant length of tube vs tuning fork wavelengths

    The graph is, I do not understand why how it is possible to find the speed of sound from the gradient for this graph. Can someone please help? Many thanks!
  6. Anish Joshi

    B Geometrical Optics: Explaining the Effects of Small Wavelengths

    Read this in my textbook:- The reason Geometrical optics works in case of formation of shadows, reflection and rarefaction is that the wavelength of light is much smaller compared to the reflecting/refracting surfaces as well as shadow causing objects that we use in day-to-day life. I...
  7. A

    I Instrument Size & Wavelength: What's the Relationship?

    What is the relationship between the size of the instrument and the wavelength you want to measure? Both in general relativity and in other areas.
  8. F

    Spectrometer sensitivity (photons/count) at different wavelengths

    Hello Everyone, I am trying to better understand how a spectrometer must be used to measure the wavelength content of the radiation from a specific source. All spectrometers measure irradiance over a wavelength range (for ex, UV-VIS) but the sensitivity (photons/count) is not the same for all...
  9. Tone L

    Optical Spectrometer centered wavelengths

    I am looking at this Hamamatsu mini-spectrometer, C12880MA [https://www.hamamatsu.com/us/en/product/type/C12880MA/index.html] The specs are, Spectral response range: 340 to 850 nm Spectral resolution (FWHM) (typ.): 12 nm Number of total pixels: 288 pixels Now the size of the band of sensor...
  10. H

    Understanding Wavelengths and Fringes: A Guide

    I think the answer is E because each bright fringe is differed by a wavelength, in other words, one wavelength is equal to 2π. (For example, the first bright fringe is d * Δy/L = 1*λ.)
  11. A

    I How do Limb-Darkening curves differ at two different wavelengths?

    Does the limb-darkening curve fall off faster at shorter wavelengths or at longer wavelengths?
  12. I

    B Particles with small Wavelengths passing through huge slits?

    I´´m confused. How can a single photon in the lightspectrum with wavelength of a few hundert nanometers go through both slits in the double slit experiment at the same time. I understand the wave- particle duality and the concepts in principle. My confusion is in the context of little wavelength...
  13. Quarinteen

    Photon wavelengths and frequencies

    Hello guys. I was thinking about solar sails and was wondering if it was possible to instead simply create a sail that is pushed by photons create something that creates an opposite force that pushes off the photons. If you did this in theory would you not be able to double the momentum? An...
  14. jisbon

    Question about whether the intensity of visible wavelengths is intensified

    Hi all, just wanted to check into check on my workings if it is correct :) So if index of lens is more than film, both rays will have phase change, and hence for constructive interference: ##2nt=m\lambda ## where n =1 and thickness = 100nm When m=1 , wavelength is 200nm m =2 wavelength is...
  15. SebastianRM

    Black Body Radiation -- why is it not at discrete wavelengths?

    I was looking at Kirchoffs Laws: "A solid, liquid or dense gas produces a continuous spectrum". I would expect objects to produce an emission spectrum since we would be observing the photons that come from spontaneous emission of electrons in excited states. This photons are specific to the...
  16. Freakyfemto

    Understanding Laser Wavelengths: A Beginner's Guide

    I don't know even where to start. In my reasoning peak florescence wavelength should be equal to its peak lasing wavelength. Is it something to do with pulse modulator (amplifier) that is used in Ti:Sapphire lasers? Or cavity length ? (But we were not given any cavity lengths). Any help would...
  17. P

    Calculating Emission Wavelength for Excited Atoms at 3.031x10^-19 J Energy Level

    Problem Statement: A sample of excited atoms lies 3.031×10^−19 J above the ground state. What is the emission wavelength of these atoms? Relevant Equations: E=hc/λ λ=hc/E I'm stuck on the first part. i.e; something / 3.031x10^-19J
  18. P

    I Atomic Electron Jump Wavelengths

    what is the shortest wavelength of light that an atom can radiate by electrons jumping shells, and longest wave length
  19. CRuff

    Detectable wavelengths of light at the surface of the Earth

    I am sure this will become a 'face-palm' moment, but can anyone point me in the direction of what electromagnetic energy wavelengths on either side of the visible spectrum, that is detectable on earth, ie what is not filtered by our atmosphere? I am specifically trying to find information on the...
  20. S

    Why do short wavelengths carry a huge amount of data not long?

    Why do short wavelengths carry a huge amount of data not long? I think this is because short wavelengths are faster o_O
  21. AlphaLibrae

    Find the wavelengths Kα, Kβ , Lα and Lβ from elemental Cu

    Homework Statement Problem: "What are the wavelengths of the characteristic Kα, Kβ , Lα and Lβ x-rays emitted from copper? Remember to use a Rydberg constant with the reduced mass correction made for elemental copper." Givens: Energy levels given: Kα (2,1) Kβ (3, 1) Lα (3, 2) Lβ (4, 2)...
  22. The Bill

    I Microphones at longer wavelengths than their size?

    Why are microphones pretty good at picking up sound that is much longer in wavelength than the size of the microphone? 1khz sound has a wavelength of around a third of a meter, varying a bit depending on atmospheric conditions. Yet a 1cm diameter electret microphone can pick it up reasonably...
  23. AGuglielmone

    B Are all wavelengths of light possible?

    I just had the thought that atoms emit light at quantized levels but that would seem to imply that only certain energy levels could possibly exist instead of a complete spectrum. But, if light is traveling down or away from a gravitational field the frequency gets shifted. Would this make it...
  24. C

    Compare the wavelengths of a photon and an electron

    Homework Statement Compare and contrast a 2.2 eV photon with a 2.2 eV electron in terms of wavelength (m).[/B] Homework Equations p = h/λ λ = h/mv The Attempt at a Solution For photon: p = h/λ λ = h/p λ = (6.63 x10-34) / (1.17 x10-27kgm/s)** λ = 5.67 x10-7 m **I have already...
  25. okandrea

    Wavelengths: Length between 2nd-order fringes

    Homework Statement Light of wavelenghs 4.80x10^2 nm and 632nm passes through two slits 0.52 mm apart. How far apart are the second-order fringes on a screen 1.6m away? λ₁ = 4.80x10^2 nm = 4.80x10^-7m λ₂ = 6.32x10^-7m d = 0.52mm = 5.2x10^-4m n = 2 L = 1.6 Homework Equations (Maxima/Bright)...
  26. F

    Medical Heating of the Human Body and Radiation Wavelengths

    Hello Everyone, Sunlight is composed of UV, visible and infrared (IR) over a wavelength range from ~290nm to ~2500nm. When we are exposed to sunlight and feel hot, is it because of the absorption of energy at the visible wavelengths and FIR, i.e . infrared wavelength much larger than 2500nm? I...
  27. C

    What is the difference between diffraction and scattering?

    Homework Statement [/B] If you hear music in the distance, would you be more likely to hear the treble or the bass notes of the music? Using your knowledge of diffraction, explain your answer. The Attempt at a Solution It would be more likely to hear the bass notes for a number of reasons...
  28. physea

    I How well can we 'see' at different wavelengths?

    Hello! There are various methods to 'see' things. Light, infrared, laser, ultrasound, magnetic field, etc. Is there a comprehensive table that will list the pros and cons, limitations and advantages, how distinctive each method can be (ie can distinguish 1mm or 1nm?), what materials they can see...
  29. Const@ntine

    Barrier of Diffraction: Different Wavelengths, Same Color?

    Hey there! We started Lab III last week, but things are a bit... strange. See, those exercises were written back in the early 1900s,and so they ask us to read from a book that was published around 1890 or so. Naturally, the library has only one copy, and it's open for 2hours per week, so it's...
  30. Const@ntine

    Thin-Film Interference (2 Wavelengths)

    Homework Statement Two glass plaques of length 10.0 cm osculate, on one end, and are separated by a wire of diameter d = 0.0500 mm on the other. Light with two wavelengths (400 nm & 600 nm) falls on one of them, and we can see it gets reflected. At which distance from the point of contact...
  31. N

    Wavelengths, Flux Density, Irradiance from a temperature measurement

    Homework Statement In my experimental setup I have a purpose built small aluminium tube that has a black layer on the inside to mimic a blackbody. The tube is heated so the inside emits as a blackbody. A separate temperature sensor attached to the tube gives the temperature of the tube. I...
  32. GAURAV DADWAL

    B Electron Color & Wavelengths: Why Dependency?

    I have read that color of light perceived by us depend on its wavelength since light is wave and also electron has wave like character that means electron has wavelength .Does that mean that electron has a color associated with it . I think its not but why .also I'm not able to understand...
  33. J

    The observed wavelengths of the hydrogen spectrum

    can be calculated using the following formula: 1/ λ = R (1/n2f - 1/n2i) Where nf and ni are integers that can have values nf = 1, 2, 3, . . . , ∞ and ni = nf + 1, nf + 2, nf + 3, . . . , ∞. Which of the following sets of integers give the wavelength of a line in the Balmer series? (Note: more...
  34. T

    I Radiation passing through Planck-scale wormholes

    This is something that has really been bugging me lately. There was a study from over twenty years ago that proposed that electromagnetic radiation might have been able to pass from one end of the universe to another in the early universe, furnishing an explanation for the homogeneity of the...
  35. ikihi

    Indices of refraction when wavelengths are given

    Homework Statement A parallel beam of light containing two wavelengths, λ1= 400 nm and λ2= 650 nm, enters the silicate flint glass (at a angle of 41 degrees, relative to normal) of an equilateral triangle (60 degrees at each angle) prism. At what angle, relative to the normal, does each beam...
  36. A

    "Seeing" particles with De Broglie visible wavelengths

    Say an electron is fired with the same De Broglie wavelength as blue light. If the electron were to reach your eye, would you see blue, or would something else happen?
  37. ThunderLight

    Why do EM waves of longer wavelengths spread out more?

    Why do longer wavelengths spread out more than shorter wavelengths? What is the physics principle/law which explains why radio waves spread out more than optic waves in free space?
  38. Cool4Kat

    How did they hear small wavelengths (high frequencies) *before* superheterodyne?

    Hi, I am researching the early history of electricity and I would love some help. So, in the very early 1900s (like 1906) there were several items created that were diodes (crystals, Fleming valve, electrolytic detector). As far as I understand, people would use these diodes to convert the AC...
  39. Kara386

    Show these wavelengths are consistent with Rydberg formula

    Homework Statement These wavelengths are emitted by a hot gas: 18.226, 13.501, 12.054 (in nanometres) Show that they are consistent with the Balmer series for a hydrogen-like atom. Which element do they correspond to? Homework Equations Rearranged Rydberg formula for hydrogen-like atoms...
  40. J

    LED Light Wavelengths: What to Know for Photolysis Prevention

    I work in a factory where we package pharmaceuticals. There are quiet a few products that are light sensitive to a certain wavelength. The lights in the older buildings are fluorescent and were have defined wavelength specification. The wavelength determined the color light/filters set in the...
  41. G

    Finding frequencies and wavelengths

    Hey! I'm struggling really badly with some physics homework, we've done nothing on this stuff in class and I can't find ANY help online and I'm stressing pretty bad right now so ANY help would be AMAZING! Here's my questions... "This question is about electromagnetic waves traveling in free...
  42. I

    Atomic Spectra of Hydrogen and Mercury

    Homework Statement Hi! I have a a question regarding the Atomic Spectra of Hydrogen and Mercury. My problem involves the value of m and Rydberg's constant. I used a spectrometer for this lab and calculated all the necessary angles. Homework Equations See below The Attempt at a Solution...
  43. R

    Uncovering Wavelengths Not Reflected in a Soap Bubble Film

    1. The problem statement, all variables and given/known da A soap bubble 500 nm thick is illuminated with white light. The index of refraction of this unique soap film is 1.35 for all colors (no dispersion). a) What wavelengths are not reflected? Homework Equations 2nt=mL 2nt=m(L/2) The...
  44. JohnGaltis

    Young's Double Slit with 2 Wavelengths variant

    Homework Statement A point light source is used in a Double Slit experiment. The light source contains two wavelengths(500nm and 600nm). Separation of the two slits d=1mm. Two sets of interference fringes are formed on a screen. Find the angles θ where bright fringes are formed for both the...
  45. DavidReishi

    B Wavelengths corresponding to fractions of nanometers?

    In terms of the electromagnetic spectrum, are there wavelengths of light corresponding to fractions of nanometers, for example, 0.5 nm, with their own photon energies? Or are whole nanometers "nature's smallests units" when it comes to the various existing wavelengths of light?
  46. velkyr

    Rayleigh criterion (two wavelengths) + diffraction grating

    Homework Statement "A source emits light with two monochromatic components of wave-lengths λ1 = 510.50 nm and λ2 = 510.90 nm. Using the Rayleigh criterion, find the minimum number of slits of a grating that must be illuminated by a beam from the source in order to resolve these components."...
  47. memoryerasure1

    B Could mixing light wavelengths effect absorption, and emissi

    -ion process. The electron when hit by light moves to a higher shell level very briefly, to either shell 1, or 2 depending on the energy of the light wavelength. So because you mixed any EM radiation, with red light which has the lowest energy, could when light, or other EM waves gets absorbed...
  48. Atominate

    Absorption Line's Different Wavelengths

    Hey Guys. If an absorption line of hydrogen was observed in the spectrum of the Galaxy, and it's wavelength was 494.9nm, and then the same line was found to be 490nm in the laboratory (in orbit around Earth), what could be drawn from that? Thanks, Atominate
  49. YamunaVargr

    Calculating wavelengths of light

    So. I need to calculate the wavelength of light that's required in order to excite the pi electrons of B-carotene from n=11 to n=13. The Length of the wavelength of L is 17.7 A. I know how to look at the particle in a box method. And I know that the wavelength of light for B-carotene is 450...
  50. Q

    What allows certain wavelengths to pass through walls ?

    Radio waves can go through walls and x Rays go through body tissue but the visible spectrum is blocked by both . Why is this the case?
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