15. P12 P13 Waves and EM Waves (Physics) Flashcards
What is the law of reflection?
Angle of incidence(i) = Angle of reflection(r)
What is a transverse wave?
The particle oscillations are perpendicular to the direction of the energy.
Give examples of transverse waves.
light, water, radio, microwave, infrared, UV, X-rays, Gamma
What is a longitudinal wave?
The particle oscillations are parallel to the direction of the energy.
Give an example of a longitudinal wave.
Sound
What is a wave?
A wave transfers energy and information from one place to another.
Define Wavelength
The Wavelength is the length of one complete wave. (the distance between two corresponding points on a wave)
Units of wavelength?
Metres (although can be measured in mm, cm or km)
Define Amplitude
The amplitude is the maximum disturbance caused by a wave from its rest position. (centre line of wave up to the peak or down to the trough)
Define frequency
The frequency is the number of waves passing a point every second.
Units of frequency?
Hertz (or Hz - must be capital H)
Define period (T)
The period is the time it takes for one complete wave to pass a point
Units of time period (T) of a wave?
seconds, s
Equation to calculate wave speed?
wavespeed = frequency x wavelength (v = f x ?) (? - lambda = wavelength)
Equation to calculate time period of a wave from the frequency?
T = 1 / f
In a longitudinal wave, the name given to areas where the particles are close together?
Compression
In a longitudinal wave, the name given to areas where the particles are spread out?
Rarefaction
What is refraction of waves?
The change in the direction of travel when a wave crosses a boundary between one medium to another due to the wave changing speed.
Water waves refract when what causes the speed of the wave to change?
Depth of the water
Light waves refract when what causes the speed of the wave to change?
Moves from one material to another of a different optical density.
The line on a ray diagram that all angles are measured from during reflection or refraction?
normal
How do you draw a normal line at the point the light strikes the mirror?
Normal line is drawn perpendicular to the surface at the point the ray strikes the surface (using a dashed line)
What happens when a wave enters a glass block from air (not along the normal)?(Wavespeed, Angle, Wavelength and Frequency)
Wavespeed slows down, ray bends towards the normal, wavelength shortens , but frequency stays the same.
What happens when a wave leaves a glass block from air (not along the normal)?(Wavespeed, Angle, Wavelength and Frequency)
Wavespeed speeds up, ray bends away from the normal, wavelength increases, frequency DOES NOT change.
What are the properties of an image formed with a plane mirror?
Upright, Virtual, Laterally inverted, same size.
What is the difference between a virtual and real image?
A real image can be formed on a screen where as a virtual image can be seen but does not actually exist.
What is the speed of sound waves in air?
330m/s although it does vary with temperature.