Wavelength & Frequency Characteristics
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Questions and Answers

What does the symbol λ represent in the context of wave characteristics?

  • Frequency of the wave
  • Wavelength of the wave (correct)
  • Amplitude of the wave
  • The speed of light

    • How is frequency (ν) defined?

  • Number of wave cycles passing a fixed point per second (correct)
  • The rate of energy transfer from one place to another
  • Distance between two successive crests
  • The length of one complete wave cycle

    • What is the relationship between wavelength and frequency?

  • Frequency is directly proportional to wavelength
  • Wavelength increases with frequency
  • Wavelength is inversely proportional to frequency (correct)
  • Wavelength and frequency are independent of each other

    • What are photons in the context of the particle model of light?

    <p>Massless particles that make up light</p> Signup and view all the answers

    What does Planck’s equation (Q = hν) indicate?

    <p>Energy of a photon is dependent on its frequency</p> Signup and view all the answers

    What is the unit of frequency?

    <p>Hertz</p> Signup and view all the answers

    Which statement correctly describes the inverse relationship between wavelength and frequency?

    <p>A longer wavelength corresponds to a lower frequency</p> Signup and view all the answers

    What is the effect of thermal excitation on photons?

    <p>It results in the emission of radiation</p> Signup and view all the answers

    What primarily causes the absorption of radiant energy in the atmosphere?

    <p>Ozone, carbon dioxide, and water vapor</p> Signup and view all the answers

    What is an atmospheric window?

    <p>Regions of the spectrum less affected by absorption</p> Signup and view all the answers

    How does scattering in the atmosphere affect remote sensing?

    <p>It reduces image contrast</p> Signup and view all the answers

    Which type of scattering involves atmospheric molecules and is influenced by the wavelength of radiation?

    <p>Rayleigh scattering</p> Signup and view all the answers

    What effect does the atmosphere have on incoming and outgoing EM radiation?

    <p>It can cause scattering, refraction, and absorption</p> Signup and view all the answers

    Why is diffuse reflectance important in remote sensing?

    <p>It measures energy reflected uniformly in all directions</p> Signup and view all the answers

    What is a primary consequence of atmospheric absorption on remote sensing activities?

    <p>It may close down remote sensing activity in certain bands</p> Signup and view all the answers

    What primarily influences the scattering of radiation in the atmosphere?

    <p>The relative size of particles and the wavelength of radiation</p> Signup and view all the answers

    What is the primary disadvantage of using radar instruments in microwave sensors?

    <p>They have difficulty identifying water bodies.</p> Signup and view all the answers

    What does the term 'apogee' refer to in satellite orbits?

    <p>The point at which the satellite is farthest from Earth.</p> Signup and view all the answers

    Which of the following factors does NOT influence the spatial and temporal coverage of imagery from a satellite?

    <p>Instruments used on the satellite</p> Signup and view all the answers

    What is the 'swath' in the context of satellite sensing?

    <p>The width of the area sensed by the satellite during its pass.</p> Signup and view all the answers

    What does the term 'nadir' refer to?

    <p>The point on Earth directly beneath the satellite.</p> Signup and view all the answers

    How is the inclination of a satellite's orbit generally measured?

    <p>In degrees from the equator clockwise.</p> Signup and view all the answers

    What is the difference between 'sidelap' and 'overlap' in satellite imagery?

    <p>Sidelap is specific to adjacent flight paths; overlap is for the same flight path.</p> Signup and view all the answers

    What defines the altitude of a satellite in its orbit?

    <p>The height from the surface of the Earth directly beneath it.</p> Signup and view all the answers

    What is a key advantage of active remote sensing?

    <p>It can operate independently of time of day or season.</p> Signup and view all the answers

    Which equipment operates on the principle of active remote sensing?

    <p>Satellite Radar Altimeter</p> Signup and view all the answers

    How does a whiskbroom scanner primarily operate?

    <p>It employs a rotating mirror to scan and build up an image one point at a time.</p> Signup and view all the answers

    What characteristic wavelength does a typical radar altimeter operate at?

    <p>13.5 GHz</p> Signup and view all the answers

    What is true about passive remote sensing?

    <p>It relies on measuring natural radiation emitted or reflected from targets.</p> Signup and view all the answers

    What happens to clear water in optical remote sensing imagery?

    <p>It appears black due to low reflectance.</p> Signup and view all the answers

    What characteristic of vegetation affects its appearance in optical remote sensing?

    <p>It reflects visible light and absorbs infrared.</p> Signup and view all the answers

    What principle does the pushbroom scanner use?

    <p>Collecting uniform images by line scanning.</p> Signup and view all the answers

    What is the primary purpose of precise image-to-image registration?

    <p>To create image mosaics and compare temporal changes</p> Signup and view all the answers

    What aspect can lead to misregistration when using location references in image registration?

    <p>Variations in solar elevations resulting in different shadow patterns</p> Signup and view all the answers

    Which resampling method uses a distance weighted average of sixteen surrounding pixels?

    <p>Cubic convolution resampling</p> Signup and view all the answers

    What are the two major radiometric corrections mentioned?

    <p>Earth-sun distance correction and sun elevation correction</p> Signup and view all the answers

    What method significantly increases the speed of spatial domain correlation in image registration?

    <p>Sequential Similarity Detection Algorithm (SSDA)</p> Signup and view all the answers

    How are pixel brightness values normalized during sun elevation correction?

    <p>Assuming the sun was at zenith during each date of sensing</p> Signup and view all the answers

    Which of the following factors does NOT influence radiance measurements?

    <p>Image format</p> Signup and view all the answers

    What is a common challenge in band-to-band registration of multispectral images?

    <p>Variability in atmospheric effects across bands</p> Signup and view all the answers

    Study Notes

    Wavelength & Frequency

    • Wavelength (λ): Distance between successive crests/troughs, measured in meters, kilometers, etc.
    • Frequency (ν): Number of wave cycles passing a fixed point per second, measured in Hertz (Hz).
    • Inverse relationship: Longer wavelengths correspond to lower frequencies.
    • Formula: λ = c/ν, where c is the speed of light.

    Particle Model of Light

    • Light is composed of photons, massless particles that transfer energy in discrete packets called quanta.
    • Energy of a photon is determined by Planck’s equation: Q = hν, where h is Planck’s constant (6.6260×10^-34 J).
    • Photons contribute to electromagnetic forces, carrying energy emitted by excited matter.

    Light Interaction with the Atmosphere

    • Atmosphere affects radiation intensity and spectral composition based on path length, energy magnitude, atmospheric conditions, and wavelength.
    • Atmosphere modifies electromagnetic radiation through scattering, refraction, and absorption.

    Absorption

    • Primarily caused by ozone, carbon dioxide, and water vapor.
    • Absorption converts radiant energy into other energy forms within the atmosphere or by targets.
    • Atmospheric windows represent spectral regions minimally affected by absorption, allowing effective remote sensing.

    Scattering

    • Scattering: Diffusion of radiation influenced by particle size relative to radiation wavelength.
    • Rayleigh scattering occurs with small particles, affecting remote sensing image quality by reducing contrast and altering spectral signatures.

    Remote Sensing Methods

    • Active Remote Sensing: Sensors transmit their own signals, measuring returned energy. These sensors operate regardless of time/season and use wavelengths not in solar spectrum.

      • Example: Satellite Radar Altimetry operates at 13.5 GHz, measures time taken for pulses to return from Earth’s surface.

    • Passive Remote Sensing: Measures natural radiation emitted or reflected by targets.

      • Examples: Advanced Very High Resolution Radiometer (AVHRR), Sea-viewing Wide Field-of-View Sensor (SeaWiFS).

    Sensor Classification

    • Based on scanning processes:

      • Whiskbroom scanners use rotating mirrors and build images point by point.
      • Pushbroom scanners utilize an array of sensing elements and capture images line by line.

    • Based on electromagnetic radiation (EMR) range:

      • Optical sensors operate from 0.3 to 14 mm, useful for meteorological and ocean monitoring. Reflectivity varies by surface type (e.g., clear water appears dark).
      • Microwave sensors penetrate atmospheric conditions, useful for detecting geological features and sea ice.

    Satellite Orbits

    • Key characteristics: orbital period, altitude, apogee/perigee, inclination, nadir/zenith, and swath width.
    • Orbital periods can vary from 100 minutes to 24 hours.
    • Altitudes classify satellites as low, moderate, or high (up to 36,000 km).

    Image Registration

    • Necessary for creating image mosaics, temporal change tracking, and multispectral image integration.
    • Automatic digital registration uses correlation for overlapping areas to minimize misregistration errors.

    Radiometric Corrections

    • Influenced by viewing geometry, instrumental response, atmospheric conditions, and illumination changes.
    • Key corrections include Earth-sun distance and sun elevation corrections to normalize pixel brightness values based on solar position.

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    Description

    This quiz explores the fundamental characteristics of wavelength and frequency in electromagnetic waves. It covers definitions, measurements, and the significance of these concepts in physics. Test your understanding of wave properties and their applications.

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