P6 - Waves Flashcards
Electromagnetic spectrum list lowest frequency - highest fruequency GO
Radio waves, micro waves, infrared, visible light, ultra violet, x-rays, gamma rays
Longitudinal waves travel perpendicular to the direction of travel
False. Transverse waves do. Longitudinal waves travel parallel to the direction of travel
What is the definition of frequency?
How many waves pass in one second
Waves transfer…
Energy
What is the opposite of compression?
Rarefaction
Which of these waves are transverse?
a) sound
b) light
c) sea
d) slinky (forwards)
b) light
c) sea
The larger the amplitude the ______ the sound
Louder
Which is the fastest wave in the electromagnetic spectrum in a vaccum?
They all travel at the same speed
Microwaves, visiable light and radio waves can all be used for communications. True or false?
True
Why does more scientific research need to go into WiFi? Give 2 reasons
It has only been around for a short period of time, so more research needs to go in to check it’s safe for people to be around
How can EM (Electromagnetic) radiation be dangerous?
When it enters a living tissue, whilst it’s often harmless, sometimes it can cause damage such as sunburn, blindness, skin cancer, gene mutation and cancer (When high frequency waves like UV, x-rays and gamma rays are emitted)
What is the units for radiation dose?
Sieverts. This is not a measure of the total amount of radiation that has been absorbed, it measures the risk of harm from the body being exposed to radiation
How many millisieverts is a sievert?
1000mSv = 1Sv
A siervert is pretty big, so it is often in millisierverts
What does a CT scan do?
Uses X-rays and a computer to build up a picture inside the patients body.
When evaluating the risk of using any type of EM radiation (mainly X-rays), what can be said about the risk for different body parts?
The risks are different in different parts of the body
Waves transfer energy where?
In the direction that they are travelling in
Give some examples of transverse waves
All electromagnetic waves
Ripples and waves in water
A wave on a string
Give some examples of longitudinal waves
Sound
Before an earthquake
Give the formula for wave speed
Wavespeed = frequency x wavelength m/s = Hz x m
How can you measure a period? What is this?
28 day– ha no, that’s biology. In physics, a period is the amount of time it takes for a full cycle of a wave
It is found with 1/frequency (in hertz)
What are the 2 different parts of longitudinal waves called?
Rarefactions - where the vibrations are spread out
Compressions - where the vibrations are close together
Give the difference between transverse and longitudinal waves
Transverse waves - the oscillations (vibrations) travel perpendicular to the direction it is travelling in
Longitudinal waves - the oscillations travel parallel to the direction it is travelling in
Also, pretty sure that longitudinal waves can involve particles colliding in that pattern - like sound, but transverse waves never have particles. They are just waves of energy
How can you measure the speed of sound?
Using an oscilloscope
It should be 330m/s
330m/s is what?
Roughly the speed of sound
How can you use a ripple tank to measure the speed of water ripples?
1) Using a vibrating bar connected to a power pack/ a signal generator attached to a dipper, submerged in a ripple tank (tray of shallow water). Also, have a light above it, and white paper beneath so that the shadows of the ripples will show on the paper
2) The distance between each shadow line is equal to one wavelength. (Should draw the ripple lines on the paper, perhaps easier to film it then slow mo or pause it). So, measure the distance between the shadow lines that are 10 wavelengths apart, then divide this distance by 10 to find the average wavelength
3) This is a good method for measuring the wavelength of moving waves or small wavelengths
4) Use wavespeed = frequency x wavelength to calculate the speed of the waves (frequency by counting waves that pass in 10 seconds, then divide by 10)
The setup is ideal, as you can measure the wavelength without disturbing the waves
All waves can be absorbed, transmitted or reflected. True or false?
True
When a wave meets a boundary between 2 materials, what 3 things can happen?
1) The wave is ABSORBED by the second material - the wave transfers energy to the material’s energy stores. Often, the energy is transferred to a thermal energy store, which leads to heating (how a microwave works)
2) The wave is TRANSMITTED through the second material - the wave carries on travelling through the new material, often leading to refraction. Can be used in communications as well as the lenses of glasses or cameras
3) The wave is reflected - where the incoming ray is neither absorbed or transmitted, but instead sent back away from the second material. How echoes are created
