Waves Flashcards
What are waves?
Waves are vibrations that transfer energy from place to place without matter(solid,liquid or gas) being transferred.
What can waves be described by?
Their amplitude, frequency and wavelength.
Some waves must travel through a substance. The substance is know. As the medium and it can be a solid, liquid or gas. They must travel through a medium, and it is the medium that vibrates as the waves travel through. Give two examples.
Sound waves and seismic waves.
Other waves travel through a vacuum- through empty spaces. Name these waves and why can they do this?
Electromagnetic waves. Light waves and radio waves can travel through a vacuum. This is because there are no particles moving in an electromagnetic wave, as these waves are oscillations in electric and magnetic fields. The oscillations are perpendicular to the direction of travel of the wave. So all electromagnetic waves are transverse.
Describe a transverse wave.
Transverse waves vibrate at right angles to the direction of energy transfer. All electromagnetic waves are transverse.
Describe a longitudinal wave
Longitudinal waves vibrate parallel to the direction of energy transfer. A sound wave is longitudinal.
What are mechanical waves?
Eg. Waves on springs, sound waves, travel through a medium (substance). Mechanical waves may be transverse or longitudinal.
When a longitudinal wave passes through air, what happens to the air particles at a compression?
They are pushed closer together.
What type of wave can be produced on a stretched string?
Transverse waves
What is the amplitude?
The amplitude of a wave the height of the wave crest or the depth of the wave trough from the position at rest.
Complete the sentence:-
The greater the amplitude of a wave the _______ _______ it carries.
More energy
What is the wavelength?
The wavelength of a wave is the distance from one crest to another.
What is the frequency? And what is its unit?
The frequency of a wave is the number of wave crests passing a point in one second. The unit is in hertz (Hz). This unit is equivalent to per seconds.
How do you work out the speed of a wave?
Using the equation. V=f x wavelength
Give the units for v, f and wavelength.
V- wave speed in m/s
F- hertz
Wavelength- metres
What is the speed of waves with a frequency of 5 Hz and a wavelength of 2m?
10m/s
What is the wavelength of a longitudinal wave?
It is the distance from middle of one compression to the middle of the next compression. This is the same as to middle of one rare fraction to there middle of the next rarefaction.
Rarefaction- stretched apart
What is a kilohertz and megahertz?
kHz is 1000 Hz.
MHz is 1,000,000 Hz.
What is the normal?
The line perpendicular to the mirror at the point where the incident ray hits the mirror.
The image in a plane mirror is: give 4 properties.
The image is the same size as the object being reflected
Upright
The same distance behind the mirror as the object is in front
Virtual
Complete:
The law of reflection states that: the angle of incidence is equal to the ________ ___ _________.
Angle of reflection
What is refraction?
Refraction of light is the change of direction of a light ray when it crosses a boundary between two transparent substances.
Complete the gaps:
When light enters a more dense substance such as going from air to glass it _______ down and the ray changes direction _________ the normal.
Slows
Towards
Fill in the gaps:
When light enters a less dense substance, such as going from glass to air, it _______ up and the ray changes direction _____ from the normal.
Speeds
Away
