# OCR 21st Century Combined Science P1

• Created by: kokokeisy
• Created on: 20-04-18 15:28
Whats a Wave?
Regular Disturbance that transfers energy.
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What happens when a wave travels through a medium?
Particles of a medium vibrate and transfer energy between each other. Patricles stay in the same place and only energy is transferred.
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Whats the Amplitude?
Displacemet from the rest position to the crest or trough.
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Whats the Wavelength ?
Disturbance between same points on two neighbouring disturbances (crest to crest)
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Whats the Frequency?
number of complete waves made by the source/cycles passing a certain point per second. Measured in Hz (Hertz)
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Whats the PERIOD of a wave?
number of seconds it takes for one full cycle to pass a certain point
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Equation for the PERIOD OF A WAVE
Period = 1 % Frequency
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WHat can the Wave Model or waves be used for?
describe and predict how one object affects the another object by transferring energy to it by waves.
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Features of a TRANSVERSE wave?
Disturbance of the medium is PERPENDICULAR (90) to the direction of the wave travels. E.G EM Waves, Waves in Water/Rope
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Features of a LONGITUDINAL wave?
disturbance of medium is PARALLEL to the direction the wave travels. They make COMPRESSIONS and RAREFRACTIONS. E.G Sound Waves
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What experiment can you do to measure the speed of sound?
Using an Oscilloscope, Signal Generator and 2 microphones.
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How would you carry out the experiment to measure the speed of sound?
Attatch signal generator to speaker to generate sound with specific frequency. Slowly move microphones away from each other. Measure DIstance between microphones for wavelength. Use Wave Speed Equation,
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In a ripple tank, what would you need to measure a frequency?
A cork and a stopwatch
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In a ripple tank, what would you need to measure the wavelength?
Strobe light and cm squared paper
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In a ripple tank, what would you need to measure the wavespeed?
Pencil, Stopwatch
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What do you need to do to ensure a fair test?
Take an average, Keep the equipment the same, Variables that arent tested are the same
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What can happen if a wave meets a boundary between two materials?
Can be ABSORBED, TRANSMITTED or REFLECTED.
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What happens during REFRACTION?
When a wave hits a boundary at an ANGLE to the normal, and the CHANGE IN SPEED causes a CHANGE IN DIRECTION.
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When a wave hits a boundary, what stays the same and what changes and how?
Frequency of a wave stays the same, but if the wave slows down, the Wavelength decreases and if a wave speeds up, the Wavelength increases.
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What waves show the behaviour of light and sound waves?
Water Waves
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How do you investigate Refelction using a Ray box and a Mirror?
Draw a 90 degree line on the normal. 2) Place a plane mirror so it lines up with the normal. 3) Shine light beam at mirror 4) Trace incident and reflected light rays
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Whats the rule between the angle of incidence and the angle of reflection?
the angle of incidence ALWAYS equals the angle of reflection
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How do you investigate the Refraction of Light?
1) SHine laser bea at an angle into a triangular glass prism. 2) TRace the incident and emerging rays. 3) Measure angles of incidence and refraction.
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WHat happens when waves enter glass through the air?
It bends TOWARDS the normal.
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WHat happens when waves leave glass?
It bends AWAY from the normal.
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What may the speed of a wave depend on?
Its wavelength.
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What speed do EM Waves travel at?
They all travel at the same speed through a vacuum.
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What do we base EM waves on to group them?
their frequency and wavelength.
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State the seven Electromagnetic Wave Spectrum.
Radio waves, Microwaves, Infra red Radiation, Visible Light, Ultra Violet, X-Rays, Gamma Rays.
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Which EM Wave has the shortest wavelength an which has the longest?
Longest- Radio Waves Gamma Rays- Shortest
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Changes in nuclei causing gamma rays to be emitted
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When bonds holding atoms together in molecules vibrate.
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What generates Visible Light, UV, and X-Rays?
When electrons drop down an energy level and emitting the energy in the form of radiation.
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What happens when UV from the SUn is absorbed.?
When absorbed by O2 molecules, it creates an ozone layer which absorbs IONISING UV RADIATION, protecting living things.
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WHat happens when an electron absorbs and emitts an EM Wave?
It moves up an energy level (excited) and goes to a partially filled/empty shell. Then it falls back to OG energy level and EM wave energy will be lost.
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What is meant when an atom is ionised? (Positive ION)
When an electron has enough energy to leave the atom/molecule.
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Why is high amounts of ionising radition exposure dangerous?
Can cause cell damage and cell destruction
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Why is LOW amounts of ionising radiation exposure danger?ous
Can make cells get uncontrolled cell division, leading to cancer.
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TRansmit information e.g television and radio shows
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What do EM Waves cause charged particle to do in a conductor?
To oscillate. It induces an alternating circuit of the SAME EM wave that induced it.
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How could you encode information using a transmitter and a reciever?
Encode info in an a.c, then transmit it as a radio wave. Wave induces an a.c. in the reciever.
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Uses of Microwaves.?
Satellites, Cooking food
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How do Microwaves heat food?
Absorbs and transfers energy to water molecules in the food heating it up.
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Detect IR Radiation and Monitor Temperature.
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How does Infra-Red detect IR Radiation?
Turns it into an electrical signal, displayed as a picture. Hotter the object, the brighter it is
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Uses of light signals?
Communication through optical fibres, Carry data over long distances, and take photos.
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Uses of Optical Fibres?
Telephone and Internet Cables. See inside the body (better than surgery)
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How do optical fibres work?
Bounce light off sides of a narrow core. Pulse of light enters the core at a certain angle and reflects till its at the other end.
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Flourescent Lights, Security Pens, UV Lamps, Tanning Salons
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Uses of X-Rays?
View internal structure of objects and materials, View bones or metal
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How are X-Rays produced to view images?
Its directed thrugh an object onto a detector plate. Its absorbed by denser material where it is viewed as a bright image.
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How are Radiographers and Patients protected from exposure to X-Rays?
Lead Aprons, Shield, and minimum exposure. (causes CELL DAMAGE)
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Uses of Gamma Rays?
Sterilise Medical instruments/Food. CancerTreatments. Medical Imaging
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How do Gamma Rays sterilise medical instruments?
When absorbed by microbes, it kills them
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Examples of Greenhouse gases?
Methane, Carbon Dioxide, Water Vapour
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What human activity factors affect the amount of greenhouse gases in the atmosphere?
Deforestation, Burning Fossil Fuels, Agriculture, Landfills, Waste from agriculture.
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What has increased the amount of CO2 in the atmosphere?
Burning of fossil fuels and deforestation.
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Whats Global Warming?
Increase in the Earths Temperature
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Why is it hard to full understand the Earths Climate>?
Theres so many variables that it makes it complex
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What has been used recently to help show causes of global warming?
Computer Models.
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## Other cards in this set

### Card 2

#### Front

What happens when a wave travels through a medium?

#### Back

Particles of a medium vibrate and transfer energy between each other. Patricles stay in the same place and only energy is transferred.

### Card 3

#### Front

Whats the Amplitude?

### Card 4

#### Front

Whats the Wavelength ?

### Card 5

#### Front

Whats the Frequency?