Waves Flashcards
General properties of waves
-transfer energy without transferring matter/ waves are also oscillations or vibrations
Wavelength
The distance between the point of a wave and the same point on the next wave
Speed of a wave/frequency
Frequency
Number of waves that passes a single point per second
Speed/wavelength
Speed
Distance travelled by a wave each second
Frequency x wavelength
Time period
Time it a takes to complete a wave or an oscillation
1/frequency
Amplitude of a wave
Distance from the center to the crest
Transverse waves
-has peaks and troughs
-vibrations are at right angles to the direction of travel
-eg:light
Longitudinal wave
-eg: sound waves
-oscillations are parallel to direction of travel
Reflection
Change in direction when a wave meets a boundary
Angle of incidence = Angle of reflection
Normal: line at 90* to surface ALWAYS MEASURE ANGLES TO NORMAL
Refraction
- change in speed of a wave when there is a change in medium (substance)
- in many cases wave will change direction
- rays enter the surface perpendicular to normal
- frequency stays the same but wavelength changes
Diffraction
-Spreading out of a wave when it meets an obstacle. An obstacle can be a gap.
-the narrower the gap, the greater the wavelength, the more diffraction
-frequency, wavelength and speed all stay the same
Refractive index in refraction (Snells Law)
n1 x sin Angle1 = n2 x sin Angle 2
N1 is always = to 1 In IGCSE
n = sin (angle of incidence)/ sin (angle of refraction)
Refractive index (n) of a medium
Speed of light in vacuum (3.0 x 10 to the power of 8 )/ speed of light in the medium
Total internal reflection
When light travels from a more optically dense (=slow) to a les optically dense medium (=fast) there is an angles called CRITICAL ANGLE, BEYOND WHICH NO LIGHT IS TRANSMITTED. All light is reflected.
Critical angle related to refractive index by: n= 1/sin c
Converging lenses
Transparent block which brings light rays together at a point called the principal focus by utilizing refraction.
Focal length: distance between the center of the lens and the principal focus.
Real images
Formed when distance of the object from the center of the lens is greater than the focal length.
Virtual images
Distance of the object from center of the lease is smaller than the focal length.
Dispersion of light
When white light passes through a glass prism, it splits up into seven colors. This happens because the different colors travel a different speeds in the glass meaning that they refract by different amounts.
Monochromatic light
Light of a single frequency nor wavelength
Electromagnetic waves
-Transverse waves
-not need medium
-speed is constant, wavelength decreases, frequency increases.
-THE HIGHER THE FREQUENCY, THE HIGHER THE ENERGY
Uses of electromagnetic waves
-radio waves (radio, television communications)
-microwaves (satellite communication, microwave)
-ultraviolet light
-X-rays
-Gamma radiation
Sound waves
Longitudinal waves created by vibrating sources. Medium is needed to transmit sound waves such as air.
- wave energy travels in same direction as particles within the wave
-higher amplitude= louder
-higher frequency= high pitch
ULTRAsound
Higher frequency than humans can hear
INFRAsound
Lower frequency than humans can hear
Human hearing range
20Hz-20 000Hz
