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OCR Twenty first century Science GCSE P1
Transcript of OCR Twenty first century Science GCSE P1
P1.2 What do we know about the Earth and how it is changing? P1: The Earth in the Universe Structure of the Earth Crust
Inner core The wave equation wave speed = frequency x wavelength Tectonic plates What drives them?
Heat from the core moves through the mantle as convection currents
Remember hot liquids and gases are less dense and rise
This transfers heat from somewhere hot to somewhere cooler P and S waves P waves
Pass through solid and liqiud
Pass through solids can't pass through liquid core
More destructive. Alfred Wegener Wegeners Clues
Jigsaw "Geometric" fit of continents
Matching fossils Vindication Scientists eventually accepted Wegener's ideas because of new evidence;
Sea floor spreading
Magnetic reversal patterns Why did others reject his theory?
Not a geologist
Was unable to measure drift
had no plausible explanation of drift Example:
Frequency = 165Hz
Wavelength = 2m
What is the wave speed?
Wave speed = frequency x wavelength
Wave speed = 165Hz x 2m
Wave speed = 330m/s The wave equation You can work out the speed of a wave if you know…..
1. How many waves pass each second.
2. How long each wave is.
(the wavelength) How fast do waves travel? LONGTUDINAL WAVES
The wave moves along in the same direction as the disturbance or vibration. TRANSVERSE WAVES
The wave moves at right angles to the disturbance or vibration. TRANSVERSE AND LONGITUDINAL We cannot see light or sound waves so looking at waves moving along a spring can help us learn more about them.
There are 2 main types of waves, they carry a lot of energy from one place to another.
The 2 types are called TRANSVERSE AND LONGITUDINAL waves. REMEMBER LAST LESSON…. 6. What is the speed of sound in water if a 5kHz* sound has a wavelength of 0.3m?
7. is the speed of a radio wave of wavelength 1500m and frequency 200kHz*?
8. What is the frequency of a radio wave of wavelength 100m and speed 300,000,000m/s?
9. What is the frequency of a microwave of wavelength 60cm* if its speed is 300,000,000m/s?
10. What is the wavelength of Rock FM if its frequency is 97.4MHz* and its speed is 300,000,000m/s?
kHz = 1000Hz MHz = 1000000Hz 1 What is the speed of a water wave if it has a frequency of 4Hz and a wavelength of 1.5m?
2 What is the frequency of a sound wave if its wavelength is 3m and the speed of sound in air is 330m/s?
3 What is the wavelength of a sound wave if its frequency is 200Hz and the speed of sound in air is 340m/s?
4 What is the wavelength of a wave in a slinky spring if its frequency is 8Hz and its speed is 6m/s?
5 What is the speed of a wave in a slinky spring if its frequency is 23Hz and its wavelength is 15cm*? Ten questions you did in class, try them again! Using your formula triangle means you can work out what equation to use if you need to find wavelength and frequency. Hz m (or km) m/s (watch this they may use km/s) wavelength frequency x Wave speed Wave speed
WAVE SPEED = FREQUENCY X WAVELENGTH
(m/s) (Hz) (m)
Hz is short for HERTZ which is the unit of measurement for frequency. The wave equation Direction of travel Vibration Wavelength –
Trough to Trough Wavelength – Peak to Peak Lesson Objectives:
To be able to identify amplitude, wavelength and frequency on a diagram of a transverse wave.
To be able to use the equation for wave speed Describing transverse waves and
the wave equation Frequency – The number of waves per second. If one wave passes in one second it has a frequency of one Hertz or Hz. This is the unit of frequency. Time (s) Height (m) 2 1 1 2 0 2 1 Direction of travel Vibration Amplitude Amplitude Wavelength Wavelength Do the calculation.
Write the answer clearly and
Don’t forget the UNITS. Put in the numbers you have been given
In the question.
Check they are in the correct positions. Write out the equation in full
Rearrange it if you need to using your
Formula triangle THREE STEPS TO EXAM MARKS Find the wave speeds….
1) Wavelength = 3m, Frequency = 100Hz
2) Wavelength = 2m, Frequency = 135Hz
3) Wavelength = 0.5m, Frequency = 200Hz
Remember the 3 step method for equations – YOU MUST DO THIS TO GET FULL EXAM MARKS!! THREE STEPS TO EXAM MARKS