P2: Waves Flashcards
What are the two types of waves?
Transverse or longitudinal.
How do the particles vibrate in transverse waves?
The particles vibrate at right angles (90°) to the direction of energy transfer.
What are the vibrations in waves known as?
Oscillations.
State some examples of transverse waves.
Water waves, electromagnetic spectrum waves, secondary waves.
Describe the vibration of particles in a longitudinal wave.
The particles vibrate in parallel with the direction of energy transfer.
What are the two types of periods that the longitudinal wave travels through?
Compression and rarefaction
State some examples of longitudinal waves.
Sound waves and seismic primary waves.
What is amplitude?
The maximum displacement of a point on the wave of the undisturbed position.
What is wavelength?
The distance from a point on one wave to the same point on the next. (Crest to crest)
What is frequency?
The number of waves that pass a point each second.
What is the period?
The time is takes for one complete wave oscillation.
What is the equation for wave speed?
Wavespeed = frequency x wavelength.
How can you measure the speed of sound waves?
Using two microphones connected to a computer. Measure the distance between the two, then make a sound. The computer calculates the time is takes for the sound wave to travel from the first microphone to the second.
What can you use to measure the speed of water ripples?
A ripple tank and a light.
What happens when a wave meets a boundary between two different materials?
The wave is either absorbed, transmitted or reflected.
What happens when a wave is absorbed?
Its energy is transferred.
What happens when a wave is transmitted?
It carries on travelling through the material.
What happens when a ray is reflected?
It travels back.
Why can’t sound waves travel through a vacuum?
Because there are no particles to vibrate.
Name the two types of reflection
Specular and diffuse.
What name is given to a reflection from a smooth surface?
Specular reflection.
What name is given to reflection from a rough surface?
Diffuse reflection
What is the correlation between the angle of incidence and the angle of reflection?
They are equal
A light ray travels through air, then a glass block, then air again. Refraction has not occurred. Why?
The incident ray of the light is along the normal (the ray is perpendicular to the glass surface - but do not remember it this way)
Compare sound waves to water waves
Sound waves are longitudinal, faster and have a higher frequency
Water waves are transverse, slower and have a lower frequency
What is displacement in a wave?
The distance that a certain point in the medium has moved from its rest position
What is the peak in a wave?
The highest point above the rest position
What is the trough in a wave?
The lowest point below the rest position
What is rest position in a wave?
The undisturbed position of the particles or fields when they are not vibrating.
How do you measure frequency using a ripple tank?
-Equipment: Stopwatch, slow-mo camera.
-Count the number of waves passing a point over 10 seconds, then divide the answer by 10.
-This is the frequency.
How do you record wavelength using a ripple tank?
-Equipment: Camera, ruler
-Measure the length of a certain amount of waves
-Divide answer by the number of waves, answer is average wavelength.
State one of the hazards, consequences and control measures from a ripple tank RPA.
-Electrical components near water
-Can cause shock and damage to components
-Secure electrical components before adding water taking care not to splash
Describe the structure of a ripple tank.
-A shallow tank of water with a long vibrating wooden rod placed in one side of the tank, connected to a power pack.
-Below the ripple tank is a piece of white paper with a ruler next to it.
-Above the ripple tank is a bright light
What is the practical of waves on a string used to measure?
Used to measure the waves in a solid
Describe the set-up of the “waves on a string” practical.
-Attach a string to a vibration generator and use a 200g hanging mass and pulley to pull the string taut. Place a wooden bridge under the string near the pulley.
-Switch on the vibration generator and adjust the wooden bridge until stationary waves can be clearly observed.
How do you measure the wavelength of waves on a string?
-Measure the length of as many half wavelengths (loops) as possible
-Divide by the number of half wavelengths (loops).
-This is half the wavelength, doubling this gives the wavelength.
How do you measure the frequency of waves on a string?
-The frequency is the frequency of the power supply.
State one of the hazards, consequences and control measures when measuring waves on a string.
-Cord may snap
-Causing damage to eyes
-So wear eye protection/place safety screen
What do electromagnetic waves transfer energy as?
Radiation.
Can electromagnetic waves travel through a vacuum?
Yes
State the order of the light spectrum.
Radiowaves, Microwaves, Infrared Radiation, Visible Light, Ultraviolet Light, X-rays, Gamma Rays.
State the uses of Radiowaves.
Broadcasting television and radio, satellite transmissions.