light & optics/ waves & sound Flashcards
Electromagnetic waves
give the equation for speed of light
give the equation for energy of light
Visible Light Spectrum
Myopia and how can it be corrected?
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Myopia is a condition in which light rays from distant objects are focused in front of the retina.
- Myopia can be corrected using diverging lenses, which spread light rays before they reach the eye to move the location of the focused image farther back in the eye onto the retina
- A diverging lens creates upright virtual images.
Diverging (concave) lens
- spreads parallel rays of light away from its focal point.
- A virtual image is formed from the apparent convergence of refracted light rays traced back to the same side of the lens as the object.
- The image is virtual because the light rays do not actually converge at the image
- vitual images are always upright NOT REAL
Hyperopia and how it can be corrected?
- causes light rays from nearby objects to be focused behind the retina
- congerging lenes correct hyperopia by bending light rays inward before they reach the eye
Converging (convex) lens
- converges parallel rays of light toward its focal point.
- A real image is formed from the convergence of the refracted light rays on the side of the lens opposite the object.
- Real images are always inverted (upside-down with respect to the object).
Dispersion of light
- Dispersion refers to the phenomenon of different frequencies of light having slightly different refractive indices.
- Light with higher frequency (such as violet light compared to red light) has a higher index of refraction in a lens and therefore refracts more.
- The formation of blurry images due to dispersion is known as chromatic aberration.
polarization of light
refers to the orientation of its oscillations in space
spherical aberration
- is due to the geometry of a spherical lens
- Light rays near the edge of a spherical lens refract more than predicted for an ideal lens.
- Because the image created with red light is focused, the blurriness did not occur due to spherical aberration.
- In addition, all frequencies of light are affected by spherical aberrations.
phase shift of a wave
- refers to its displacement from another wave
- phase shifts (or lack thereof) in light do not affect its refractice properties
Snell Law (refraction)
Geometry of right triangles
Diverging lenses
for converging lenses, when is there NO image formed?
no mage is formed if the object is at the focal point of the lens
Light rays exactly 1 focal length from the lens will be refracted by the lens to become parallel and never converge/diverge to an image.
Snell’s Law may be used to predict ?
- Snell’s law may be used to predict the relationship between the angle of incidence and angle of refraction provided that the relationship between the refractive index of each medium is known.
- Light will bend toward the normal when it passes through a media interface from lower to higher refractive index.
Sinusoidal functions
Total internal reflection
may only occur when light leaves a medium with a HIGHER refractive index & enters as medium with a LOWER refractive index
Single-Slit Diffraction
- Single-slit diffraction is an optical phenomenon that demonstrates the waveform nature of light.
- diffraction is broadly defined as the bending of light around edges or objects
- The band pattern associated with a given diffraction event is related to slit width (a in the equation) and the wavelength of light.
Wave interference
when the path lengths of two light waves differ by wavelenght /2, the waves arrive at the background ____________
as a result,_____________________occurs such that dark bans in the diffraction pattern are produced
- out-of-phase (i.e the peak of one waveform coincides to a trough of the other)
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destructive interference
- conversely, light bands result from zero or minimal destructive interference
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Dark bands (minimum light intensity) due to destructive interference occur when diffracted light waves pass through the slit at angles (θ) that are a function of the slit width and an integer multiple (m = ±1, ±2, ±3…) of the wavelength: sin θ= mλ/ a
- According to this relationship, decreased slit width or increased wavelength tends to widen the band pattern such that greater distances are present between light and dark bands.
- Conversely, increased slit width or decreased wavelength results in a relatively narrow band pattern.
- Therefore, both slit width and wavelength influence the angle of propagation associated with the dark and light bands in the pattern of diffracted light
Band pattern
properties of sound
- Sound propagates through the vibrations of the molecules as longitudinal pressure waves, and therefore cannot exist in a vacuum (becuase sound propagates through vibrations of the molecules in a medium)
- The attenuation of sound is greatest in soft materials (damping, decreasing in the amplitutde/intesity of a wave due to absorption & scattering) and increases with distance.
- Sound travels most slowly in gases and most quickly in solids.
image:
compressions are areas of high pressure
rarefactions (areas of low pressure)
Longitudinal Waves & transverse waves
Decibel Scale
- The decibel (dB) scale is logarithmic and relates the perceived loudness of a sound to its actual intensity.
- For each 10-fold decrease, sound intensity decreases by 10 dB. Therefore, a 100-fold decrease in sound intensity corresponds to a decrease by 20 dB.
Doppler Effect
- The Doppler effect occurs when the observed frequency and wavelength of a sound are shifted from those of the original due to relative motion between the source and the observer.
- The frequency shift is positive when the source velocity is negative (moving closer) and negative shift when the source velocity is positive (moving away).
How is sound propagated?
- sound is propagated in the form of pressure waves (longitudial waves of oscillating pressure) by the vibrations of the molecules in a medium
- the rapid expansion and contraction of crystals creates pressure waves (sound) by the vibrating nearby particles
Wave properties
List of prefixes
Derived SI units that are the same, like Hz is s-1, this flashcard is a table of all SI units
Electromagnetic waves
intensity of electromagnetic radiation increases with
higher individual photon energy & higher emission rate
In which of the given scintillation materials will light travel the slowest?
- Answer: Lu2S3Ce
Explained:
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Light travels fastest in vacuum and it slower in transparent materials. The ratio of the speed of light in a vacuum c to the speed of light in a material v is the material’s index of refraction v= c /n.
- velocity is inversely proportional to index of refraction
- Therefore, the higher the index of refraction, the slower light travels through a material.
Constructive & Destructive Interference
- Constructive interference occurs when the sum of amplitudes results in a larger amplitude.
- Destructive interference occurs when the sum of the amplitudes results in a smaller amplitude.
- A wave that is combined with a copy of itself that has been flipped across the x-axis would result in complete destructive interference.
- Complete noise cancellation occurs when the generated sound wave destructively interferes with the original wave at all points, resulting in an amplitude of zero. A wave that is flipped across the x-axis will have equal and opposite amplitudes at each point along the wave. The sum of two equal and opposite amplitudes is zero, resulting in total destructive interference and canceling all noise.
Phase shift of a wave
- The phase of a wave is the measure of the horizontal offset from a reference wave.
- When the given wave is superimposed with a copy of itself shifted by half a wavelength, it will be only partially canceled.
When a wave is superimposed with a copy of itself with double the frequency, what occurs?
- The frequency of a wave is the number of cycles that pass a fixed point per unit time.
- When a wave is superimposed with a copy of itself with double the frequency, both constructive and destructive interference can occur.
When sound passes from air to the tympanic membrane, what changes occur to the sound’s intensity and velocity?
- answer: intensity decreases; velocity increases
- When sound moves from one medium to another, a portion of its energy is reflected, decreasing its intensity. The propagation velocity of sound depends on the medium and is slowest in gases, faster in liquids, and fastest in solids.
- frequecny does NOT CHANGE, the change in velocity are only due to wavelengths, the propagation of sound waves depends on the properties of the medium
- Velocity increases with temperature.
- Velocity is slowest in gases, faster in liquids, and fastest in solids.
- Within a phase of matter, velocity increases with stiffness and decreases with density.
- _v = wavelength * frequency_
Tympanic membrane, ear structures
Resonant frequency
- The resonant frequency of an object is the frequency that causes relatively large oscillations compared to other frequencies. The fundamental frequency is the lowest resonant frequency, and each subsequent harmonic frequency is a multiple of the fundamental frequency.
- Resonant frequency waves are known as standing waves because the locations of the nodes and antinodes do not change.
- Nodes occur at the locations of zero displacement, and antinodes occur at the locations of maximum displacement.
The resonant frequency of a pipe depends on ?
pipe opened on both ends
- The resonant frequency of a pipe depends on the length of the pipe and if the ends are closed.
- A closed end has a node (zero displacement) and an open end has an antinode (maximum displacement).
- example a stethoscope that is described as a pipe open at both ends for which the pipe’s length is one half the wavelength of the fundamental frequency: L = wavelength/ 2
a pipe closed on one end
