P1 - Waves Flashcards
What is wavelength?
The length of a full cycle of the wave (eg. from crest to crest) in metres
What is amplitude?
The displacement of the wave from the rest (middle) to the crest (top) in metres
What is frequency?
The number of complete waves passing a certain point every second measured in Hz (s^-1)
What are the 2 types of waves?
Longitudinal
Transverse
What is transverse wave?
A wave where the vibrations are perpendicular to the direction of energy transfer of the wave
Which types of wave are transverse?
All EM waves
Water ripples
What is a longitudinal wave?
A wave where the vibrations are parallel to the direction of energy transfer of the wave
What is the formula that links wavelength and frequency?
Wave speed (m/s) = frequency * wavelength
Which types of waves are longitudinal?
Sound waves and ultrasound
Shock waves
What are the 3 ways that the direction of travel of a wave can be changed?
Reflection
Refraction
Diffraction
Why can we see objects?
Because different light rays reflect off different objects and go into our retina
How does changing the surface affect the reflection of light rays off it?
An uneven surface causes light to reflect off in all directions so we can’t see a clear reflection
A smooth and shiny surface reflects all of the light rays in one direction meaning that we can see the reflected image
What is the law of reflection?
Angle of incidence = angle of reflection
What is the angle of incidence?
The angle between the normal (imaginary line perpendicular to the surface) and the incident ray (the light ray approaching the mirror)
What is the angle of reflection?
The angle between the reflected light ray and the normal
What 4 things is the reflected image and why?
Same size as the object (it is as far behind the mirror as the object is in front)
Virtual (appears to be behind the mirror)
Upright
Laterally inverted (the left and right sides are swapped)
Describe how you draw a ray diagram for an image reflected in a mirror
Draw the reflected image on the other side of the mirror to the actual object (exactly as far away)
Draw an eye looking at the mirror from an angle
Draw the reflected ray coming from the virtual object to the top of the eye with an arrow on the ray to show this (dotted line for the virtual side of the mirror)
Draw the incident ray coming from the real object to the point where the reflected ray and mirror meet (add an arrow on the ray to show this)
Do the last 2 steps again but where the reflected ray meets the bottom of the eye
What is diffraction?
If the wavelength of a wave is longer than the size of a gap that it has to go through, the wave will spread out when it emerges from the gap
What 2 factors affect the amount of diffraction?
The narrower the gap, the more the wave spreads out
The longer the wavelength, the more the wave spreads out
What does maximum diffraction look like?
The emerging waves look like semi-circles
How is a diffraction diagram drawn?
Lots of parallel vertical lines on the left side of the gap and lots of curved, spread out waves on the right
What is refraction?
When a wave crosses the boundary between 2 substances, it changes direction
What happens if the wave hits a boundary face on?
No refraction occurs
What happens when a wave hits the boundary at an angle?
The wave bends towards the normal
What causes refraction?
When the wave suddenly changed to a medium that has a different density, it changes speed accordingly and this changes the direction of the wave
Describe a diagram of refraction
The incident ray hits a glass block (or other more dense medium) and the ray bends towards the normal and is called the refracted ray
When the refracted ray emerges from the fender medium, it travels away at the same angle as the angle of incidence and is called the emergent ray
