Waves, Sound and Light Flashcards
Wave
Add disturbance that carries energy from one place to another
Transverse Waves
Waves in which the direction of vibration is perpendicular to the direction of travel of the wave
Longitudinal waves
Waves in which the direction of vibration is parallel to the direction of travel of the wave
Mechanical wave
The vibration of particles. It needs a medium in which to travel. It is a series of vibrations passing from molecule to molecule in the medium
Electromagnetic wave
Does not need a medium to travel it is the vibration of the electric and magnetic fields. It travels through a vacuum at the speed of light
EM spectrum long->short
Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays
Travelling wave
Travels from the source producing it transfig energy to all the places through which it passes. Mechanical or electromagnetic
Crest
Highest point of a transverse wave
Trough
The lowest point of a transverse wave
An oscillation
One complete vibration of the source
Wavelength
The distance between two corresponding parts of a wave
Frequency
Number of waves passing a point per second
Amplitude
The maximum displacement of a wave from its mean position
Periodic time
Time taken for a wave to complete one oscillation T=1/f
Velocity of a wave
The distance travelled by any point on the wave in one second v=fλ
Reflection
The bouncing of waves of obstacles in their path
Refraction
The changing of direction of a wave when it goes from one medium to another
Interference
The edition of two or more waves, forming a single resultant wave
Coherent sources
Waves that are in phase and have the same frequency
Constructive interference
When two or more waves combine resulting in a single wave of greater amplitude than the source waves
Destructive interference
When two or more waves combine resulting in a single wave of a smaller amplitude than the source waves
Diffraction
The spreading out of a wave into a space beyond the gap or around an obstacle
In phase waves
When the crests from one source meet the crests from another
Out of phase waves
When the crests from one source meet the troughs from another
Polarization
When the vibrations are restricted to one plane only
Stationery wave
Formed when two waves of equal amplitude and frequency moving in opposite directions meet
Nodes
Points on a stationary wave that remain at rest
Antinodes
Points on a stationary wave that vibrates with maximum amplitude
Doppler effect
The apparent change in frequency our wave due to the relative motion of the source and the observer
Sound
A form of energy that travels by longitudinal mechanical waves produced by vibrating objects. Requires a mediums travel through
Acoustics
The study of sound
Natural frequency
The frequency that a body vibrates at when free to do so
Resonance
The rapid amplification of oscillation when a periodic force is applied at the same frequency as the natural frequency of the body. Results in the maximum energy transfer between the force and the object
Fundamental frequency
The lowest natural frequency of a vibrating object
Harmonics
Multiples of the fundamental frequency
Frequency limits of audibility
The highest and lowest frequencies that can be heard by a normal human ear. Between 20 Hz and 20,000 Hz
Sound intensity
The energy per second passing through a unit area perpendicular to the direction in which the sound is traveling
I = P/A
Sound intensity level
Compares a particular sound intensity to the threshold of hearing. Measured in decibels. If the sound intensity doubles the sound intensity level increases by 3 dBs
dB(A) scale
A sound intensity level scale that has been adapted for the ears frequency response
Quality of a note
Describes the shape of the sound waves, depends on the number and amplitude of the harmonics present. Music has periodic waveform and related frequencies. Noise has varying frequency with no repetition in waveform
Light
Form of energy that travels by electromagnetic waves. Can be detected by the human eye. Has a wavelength between 700 nm and 400 nm
Infra Red light
Emitted by warm objects. Can be detected by its heating effect on a blackened thermometer bulb. It affects photographic plates. Longer wavelengths than visible light
Fluorescence
When a substance absorbs UV radiation and re-emits it as visible light
Parallax
The relative movement of two objects due to the movement of the observer
Monochromatic light
Light of one colour only (one wavelength)
Diffraction grating
A piece of transparent material the large number of parallel opaque lines drawing it so that the space is between the lines act as sits to allow light through
The grating constant (d)
The distance between adjacent lines d = 1/Lines per metre
Self luminous object
Produces its own light like the sun/stars
Reflection of light
The bouncing of light off the surface of an object
Laws of reflection
- The incident ray, the normal and the reflected ray all lie on the same plane
- The angle of incidence equals the angle of reflection
Real image
Formed by the actual intersection of light rays
Virtual image
Formed by the apparent intersection of light rays
Refraction
The bending of lice as it passes from one optical medium to another
Laws of refraction
- The incident ray, the normal and the refracted ray are lie in the same plane
- The sign of the angle of incidence is proportional to the sign of the angle of refraction, for a given pair of media (Snell’s law)
Refractive index
The ratio of the sine of the angle of incidence to the sine of the angle of refraction when light travels from air into the substance
n = (refraction)
sin i/sin r
1/sin C
Real depth/apparent depth
c/v
Critical angle (C)
The angle in the denser of two media when the angle in the less dense medium is 90°
Total internal reflection
When lice is reflected back from a boundary between two Media. it occurs when the light is traveling towards a rarer medium from a denser one striking the boundary with an angle of instance greater than the critical angle
Optic fibre
A very thin strand of transparent material through which light travels by total internal reflection
Power of accommodation
The ability of the eye to focus on objects at different distances by changing the shape of the lens
Lens
A piece of carefully cut transparent material that allows light through it
Power of a lens
Inverse of the focal length
Compound lenses
Combinations of two or more lenses in contact with each other. The sum of the individual powers
Myopia
Short sightedness. Means distance objects cannot be seen clearly
Hyperopia
Long sightedness. Means near objects cannot be seen clearly
Magnification of an image
The ratio of image distance to object distance
v/u
Dispersion
The separating out of the different wavelengths of light
Primary colours
Three colours combining to form white light. Red green and blue
Secondary colours
Formed when two primary colours are mixed in equal proportions
Red blue = magenta
Red green = yellow
Bluegreen = cyan
Complimentary colours
Pairs of primary and secondary colours that combined the form white light
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