Revision 2 Flashcards
What are transverse waves?
Transverse waves vibrate at 90° to the direction of energy transfer
E.g all electromagnetic waves
What are longitudinal waves?
Longitudinal waves vibrate parallel to the direction of every transfer.
E.g sound sound waves
The vibrations are known as compressions and rarefactions
Mechanical waves
Mechanical waves which need a medium to travel through may be transverse or longitudinal
E.g waves on a slinky Spring
Amplitude
The amplitude of a wave is the height of the wave crest from the position of rest.
Frequency
The frequency of a wave is the number of wave crests passing a point in one second
Unit : hertz
Wavelength
The wavelength of a wave is the distance from one wave crest to another.
The wave equation
Speed(m/s)= frequency(Hz) x wavelength(m)
Transparent
Objects that are transparent transmits all light.
Translucent
Transmits some light
Opaque
Objects which don’t transmit light are said to be opaque.
Why are shadows opaque?
Light rays travel in straight lines. This is why the shadows of opaque objects are very well defined.
How is the normal line drawn?
The normal line is a line drawn perpendicular to the mirror.
What are waves used for?
Waves are used to transfer energy and information.
Light Ray reflected by a plane mirror
The angle of incidence = the angle of reflection
The angle of incidence = the angle between the incident Ray and the normal
Real image
A real image can be projected onto a screen.
Virtual image
A virtual image only exists in the mirror.
In a plane (flat) mirror, the image is _____, virtual and the same size as the object.
Upright
Reflection from a ____ surface in a single direction is called _______ reflection
- Smooth
2. Specular
Reflection from a ______surface causes______ .This is called _____reflection.
- rough
- Scattering
- diffuse
White light contains ___ the colours of the visible spectrum
All
The colour of an object depends on the colour that it____ and the colour that it____.
- reflects
2. absorbs
The three primary colours
Red,green and blue
Combining two of the primary colours creates a________colour.
Secondary
A coloured filter allows some colours to pass through it and absorbs the rest. We see the colour that the filter______.
Transmits
Refraction is the_____________ of waves when they travel across a boundary.
This change in direction is due to a_______.
- Change in direction
2. Change in speed
When light passes__________ the angle of refraction(in the glass) is___ than the angle of incidence
- form air into glass
2. less
Diffraction is the________of waves when they pass through a gap or round an obstacle.
Spreading out
The________the gap, the greater the diffraction
Narrower
The gap must be a_____ _____ to the wavelength of the wave in order for diffraction to take place. This why light cannot diffract round an open doorway but sound can.
Similar size
If radio waves ___ ______ _____ when they go over hills, radio and TV reception will be poor.
Do not diffract enough
The frequency range of the normal human ear is from about____ to_____.
- 20Hz
2. 20 000Hz
Sound waves are vibrations that travel through a_____(substance).
They cannot travel through a_______.
- Medium
2. Vacuum
Echoes are due to sound waves______from a hard,smooth surface
Reflected
Refraction takes place at the boundaries between layers of air at_______ _________.
The warmer the air the_______ the speed of sound.
- different
- temperatures
- greater
At night you can hear sound a long way away from its source because sound waves______ _______to the ground.
Refract back
The______of a note increases if the frequency of the sound waves increases.
Pitch
The loudness of a note increases if the_________of the sound waves increases
Amplitude
A microphone converts______ _____ to an_______ _______. This can be displayed on an oscilloscope.
- sound waves
2. electrical signal
