Waves and electromagnetic waves Flashcards
What are waves used for?
Transferring energy and information.
What are transverse waves? Why do they include electromagnetic waves?
Transverse waves oscillate perpendicular to the direction of energy transfer of the waves. Ripples on the surface of water are transverse waves, So are all electromagnetic waves.
What are longitudinal waves?
Longitudinal waves oscillate parallel to the direction of energy transfer of the waves. Sound waves in air are longitudinal waves.
What are mechanical waves and what do they need?
Mechanical waves can be transverse or longitudinal waves but they need a medium to travel through.
What is the wavelength of a wave?
The distance from a point on the wave to the equivalent point on the adjacent wave.
What is the amplitude of a wave?
The distance from the wave’s equilibrium position to its highest point or lowest point.
What do we call the top and bottom of a wave?
The maximum displacement of a point on the wave from it’s undisturbed position. (the bigger the amplitude of the waves, the more energy the waves carry)
What is the frequency of a wave?
The number of waves passing a fixed point every second.
What is the speed of a wave and what is it’s formula?
Wave speed m/s = frequency Hz x wavelength m
What is reflection of a wave?
hen a wave bounces off a surface (like a barrier), it changes direction but stays in the same medium. The angle of reflection equals the angle of incidence.
What is refraction of a wave?
When a wave passes from one medium to another (like from deep water to shallow water), it changes speed and direction. The wave bends because its speed changes, but the frequency stays the same.
What are sound waves?
Vibrations that travel through a medium. Sound waves cannot travel through a vacuum eg in space
What do we need to investigate waves?
A ripple tank for water waves, a stretched string for waves in a solid (the string) and a signal generator and a loudspeaker for soundwaves.
Why is there a delay when hearing an echo?
Because the sound waves take time to travel to the wall and back.
How do you calculate the speed of sound in air?
Speed s = distance to the wall and back 2d / time delay t
What is a primary wave? P wave
A seismic wave that causes the initial tremor and lasts one minute. They are longitudinal and push and pull material through the earth
What is a secondary wave? S wave
A seismic wave that causes more tremors and last a few minutes, occurring after. They shake the rock they pass through from side to side. They are transverse and cannot pass through the molten outer core of the earth.
What is a Long wave? L wave
A seismic wave that are the last waves to appear in an earthquake and move everything it passes through up and down and back and forwards; they travel slower than the other waves and only happen in the earth’s crust
What makes up the electromagnetic spectrum, in order of big wave length and low frequency to small wavelength and high frequency?
Radiowaves, microwaves, infrared radiation, visable light, ultraviolet, X rays, gamma waves
Name two uses for electromagnetic waves in daily life? What does the energy they produce rely on?
Microwave ovens and radiant heaters
How do you work out the speed of electromagnetic waves?
Wave speed m/s = frequency Hz x wavelength m
Explain the trends of wavelength, frequency and energy along the electromagnetic spectrum
The shorter the wavelength, the higher the frequency. The energy of an electromagnetic wave increases as the frequency increases (high frequency). So energy along this spectrum goes from low to high (wavelength high to low, frequency low to high).
