P2- Waves Flashcards
What are the two types of waves?
Transverse and longitudinal
What type of vibration do transverse waves have?
Sideways oscillations that are perpendicular (at 90 degrees) to the direction of energy transfer
What are some examples of transverse waves?
Most waves
Electromagnetic waves
Ripples and waves in water
A wave on a string
What type of vibrations do longitudinal waves have?
Oscillations that are parallel to the direction of energy transfer
What are some examples of longitudinal waves?
Shock waves in the air (ultrasound)
Shock waves such as some seismic waves
Which direction do waves transfer energy in?
The direction that they are travelling
What is the amplitude of a wave?
The maximum displacement of a point on the wave from its undisturbed position
What is the wavelength of a wave?
The distance between the same point on two adjacent waves such as between the trough of one wave and the trough of the wave next to it
What is the frequency of a wave?
The number of complete waves passing through a certain point per second
What is frequency measured in?
Hertz or Hz
1 Hz is 1 wave per second
What is the period of a wave?
The amount of time it takes for a full cycle of the wave
How do you find the period of a wave?
T (Period) = 1/f (Frequency)
What is wave speed?
The speed at which energy is being transferred or the speed the wave is moving at
What is the equation for wave speed?
Wave speed = Frequency x Wavelength
What three things can happen when a wave arrives at a boundary between two different materials?
They can be absorbed by the material, transmitted through the material or reflected off the material
What happens when a wave is absorbed at a boundary?
The wave is absorbed by the material, this transfers energy to the materials energy stores, this is how a microwave works
What happens when a wave is transmitted at a boundary?
The waves are transmitted meaning they keep on travelling through the new material which often leads to refraction
What is the rule when a wave is reflected at a boundary?
Angle of incidence = Angle of reflection
What are the two types of reflection?
Specular and diffuse
What is the difference between specular and diffuse reflection?
Specular is when a wave is reflected in a single direction by a smooth surface whilst diffuse is when a wave is reflected by a rough surface and scatters in lots of different directions
Can you list the EM wave spectrum in order?
Radio waves
Micro waves
Infra red
Visible light
Ultra violet
X rays
Gamma rays
What increases and decreases as you go along the EM wave spectrum?
Frequency increases and wavelength decreases
How do the speeds of EM waves vary?
They all travel at the same speed through air or a vacuum
What is refraction?
Waves changing directions at a boundary
What are radio waves used for?
Communications such as bluetooth and the radio
What are microwaves used for?
Satellites and microwave ovens
What is infrared used for?
To increase temperature
Cooking
To monitor people through temperature
What is visible light used for?
Transmitting data
What is ultraviolet used for?
Tanning beds
Fluorescent lights
What are X and Gamma rays used for?
Radiography to take pictures of bones
Radio or chemotherapy
Medical tracers
How do doctors protect themselves from X and Gamma rays?
Lead aprons
Lead screens
Leaving the room
How is UV harmful?
Can cause skin cancer
How are X and Gamma rays harmful?
Ionising radiation can cause gene mutation or cell destruction and cancer
Why can UV, X rays and Gamma rays be harmful?
They are high frequency waves so they transfer a lot of energy
What are the primary colours of light?
Pure red, green and blue
What happens when all the colours of light are put together?
It creates white light
What happens when light hits an opaque object?
They do not transmit light, when visible light waves hit them they absorb some wavelengths of light and reflect others
Why are some opaque objects primary colours?
Which wavelengths of light are most strongly reflected, a red apple is red, because red is the most reflected
Why are some opaque objects non primary colours?
The light most strongly reflected is that colour or colours mix to make that colour
Why are some opaque objects white?
They reflect all wavelengths of visible light equally
Why are some opaque objects black?
They absorb all wavelengths of visible light
What do transparent and translucent objects do when light hits them?
They transmit light, not all light that hits the surface is absorbed or reflected, some can pass through the object
What do colour filters do?
They only let through particular wavelengths and filter out others so only certain colours are transmitted
What happens if white light is shone at a blue colour filter?
Only blue light is transmitted and the rest is absorbed
What happens if red light is shone at a blue colour filter?
It is not transmitted so the object behind it appears black
What happens to infrared emitted when an object is hotter than its surroundings?
More is emitted than is absorbed as it cools down
What infrared is emitted when an object is at a constant temperature?
The radiation is emitted at the same rate it is absorbed
What colours and textures are better at absorbing and emitting infrared?
Black is better than white and matt is better than shiny
What is a black body?
An object that absorbs all of the radiation that hits it, no radiation is reflected or transmitted,it is the ultimate emitter
How does radiation affect the Earths temperature?
During the day lots of light radiation is transferred from the sun and absorbed causing a temperature increase
What causes sound waves?
Vibrating objects
Why can’t sound waves travel in space?
Because it’s mostly a vacuum meaning there are no particles to move or vibrate
How do you hear sound?
Sound waves reach your eardrum causing it to vibrate, the vibrations are passed on to bones in your ear called ossicles, through the semicircular canals and to the cochlea where the vibrations are turned into electrical signals which are sent to your brain
When are sound waves reflected and refracted?
Reflected by hard surfaces and refracted as they enter different media such as speeding up in denser materials
