SP4 Waves Flashcards
What do waves transfer
Energy and information but not matter
Two types of waves are
Transverse and longitudinal
Examples of transverse waves
Water surface waves
Seismic S waves
All electromagnetic waves (light, heat, radio, micro, x rays, UV, gamma)
Examples of longitudinal waves
Sound waves
Seismic P waves
What are transverse waves
Waves where the vibrations are at right angles to which the direction the waves is travelling. The particles move up and down
What are longitudinal waves
Waves where the vibrations are parallel to the direction which the wave is travelling e.g in a sound wave. Particles move backwards sand forwards in the direction of travel.
What is the equation relating wave speed, frequency and wavelength
Wave speed = frequency x wavelength
What is the wave speed when the frequency=100 and the wavelength=8
800 (m/s)
What is the equation relating wave speed, distance and time.
Wave speed = Distance / time
What is the wave speed of a wave with a distance=300 m and a time of 3 s
100 (m/s)
Describe how to measure the velocity of sound in air.
170m =
Divide the distance in metres by the average time in seconds.
For example 170 metres divided by 0.50 seconds = 340 m/s
What is refraction.
Refraction is the change in direction of a wave passing from one medium to another caused by its change in speed.
Describe how the direction of a wave changes when it goes from one material to another.
Waves change speed when they pass across the boundary between two different substances, such as light waves refracting when they pass from air to glass. This causes them to change direction and this effect is called refractio
Explain some effects of the refraction of light
Light waves change speed when they pass across the boundary between two substances with a different density , such as air and glass.
Explain how a change in wave speed can cause a change in direction.
Waves change speed when they pass across the boundary between two different substances, such as light waves refracting when they pass from air to glass.
Describe some effects of waves being reflected.
The reflection of sound causes echoes.
The law of reflection states that:
angle of incidence = angle of reflection
For example, if a light ray hits a surface at 32°, it will be reflected at 32°.
Describe some effects of waves being absorbed or transmitted.
When waves are absorbed by a surface, the energy of the wave is transferred to the particles in the surface. This will usually increase the internal energy of the particles. When white light shines on an opaque object, some wavelengths or colours of light are absorbed.
Describe how changes in velocity, frequency and wavelength are related when sound waves go from one medium to another.
When sound waves move from one medium to another, there will be changes to the velocity (or speed), frequency and wavelength of the sound wave. … the wavelength of the sound wave decreases. the frequency of the sound wave stays the same. the velocity of the sound wave decreases (since wave speed = frequency × wavelength)
List the parts of the human ear, in the order in which they transmit vibrations.
Ear canal, Eardrum, Hammer, Anvil, Stirrup (Ossiciles), Cochlea, Auditory nerve
Function of the Eardrum
Transfers vibrations from air to bones
Function of the Cochlea
Convert vibrations into nerve impulses
Function of the Ear canal
Channels sound waves into the head
Function of the Ossicles
Transfers vibrations from the eardrum to the cochlea
Function of the Auditory nerve
Transmits nerve impulses to the brain
Function of the Tiny bones (Hammar)
Amplifies vibratins
Describe how sound waves in air are converted to vibrations in solids.
Sound waves can travel through solids causing vibrations in the solid. Within the ear, sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound. The conversion of sound waves to vibrations of solids works over a limited frequency range. This restricts the limits of human hearing.
Describe some factors that affect how well sound waves transfer energy to solids.
The stronger the particle interactions are, the more quickly the wave is transferred. So in general, sound travels faster in solids than in liquids, and faster in liquids than in gas. Temperature actually increases the speed of sound, because warmer particles generally move at a faster rate.
Explain why the human ear can only detect a certain range of frequencies.
The range of frequencies that a person can hear depends on the range of lengths of hairs in the cochlea. As a person ages, the shorter hairs that respond to higher frequencies stop working - this means that people tend to lose the ability to hear higher frequencies of sound as they grow older.
What is the depth of water equation
Distance = Speed x time
What frequency is classed as ultrasound
20,000 Hz
Explain how ultrasound is used in sonar.
Sonar equipment carried on ships or submarines which uses a pulse of ultrasound. This used to detect fish or depth of the sea.
Describe uses of ultrasound in body scanning.
Ultrasound can be used for imaging inside the body. This is used for pregnant women’s to track how the fetus is developing. A gel is used to stop the ultrasound reflecting from the skin. The probe emits and receives ultrasound waves. Some sound is reflected when the ultrasound waves pass into a different medium, such as fat or bone.
What frequency is classed as infrasound
Below 20 Hz
Describe some uses of infrasound.
Infrasound can be used to investigate the internal structure of our planet. Earthquakes produce very powerful seismic waves that can be classed as infrasound waves. Seismic waves from large earthquakes are detected around the world.
What are seismic waves
Vibrations caused by the earthquakes energy that is released
What is a P wave and what can it travel through
A P wave is a sound wave traveling through rock. In a P wave, the rock particles are alternately squished together and pulled apart (called compressions and dilatations), so P waves are also called compressional waves. These waves can travel through solids, liquids, and gases as shown by their shadow zone on the earth.
What is a S wave and what can it travel through
An S wave, or shear wave, is a seismic body wave that shakes the ground back and forth perpendicular to the direction the wave is moving. . They can propagate through solid rocks because these rocks have enough shear strength. The shear strength is one of the forces that hold the rock together, preventing it from falling into pieces. Liquids lack shear strength.
Explain how seismic waves can help us to investigate the Earth’s core.
Refractions between layers cause two shadow zones, where no P waves are detected – the size and positions of these shadow zones indicate there is a solid inner core.
