Flashcards in Waves Deck (90):
What is a wave?
A wave is a transfer of energy of information from one place to another.
What causes waves?
Vibrations cause waves.
What are the two types of waves?
Transverse waves and longitudinal waves.
What do transverse waves look like?
They oscillate up and down and travel at right angles to the vibrations which caused.
What do longitudinal waves look like?
They travel in the same direction as the vibration which caused them.
What are examples of transverse waves?
-Electromagnetic waves (e.g. Light)
-slinky that's bring moved up and down
-waves on strings
What are examples of longitudinal waves?
-slinky that's being pushed back and forth
What is one complete wave?
All the way up and then down and then back yo the start point
What is the peak of a wave?
The maximum positive displacement.
What is the trough of a wave?
The maximum negative displacement.
What is a wavelength?
The distance between two like points
E.g. Peak to peak
E.g. Trough to trough
What is the amplitude of a wave?
The distance between the equilibrium line (0 displacement) and the maximum displacement of a wave (usually the peak).
What is the time period?
The time taken for one complete wave cycle is the time period (T).
What is time period measured in?
What is frequency.
The amount of waves which pass a point in one second.
What is frequency measured in?
It's measured in number per second which is called Hertz (Hz).
What is the type of relationship that frequency and time period have called?
A reciprocal relationship.
What is the equation linking frequency and time period?
What is the equation for wave speed?
Wave speed = wavelength ❌ frequency
v=f lander(symbol goes here) f
What is the unit for speed?
Meters per second
What is another equation for wave speed?
Wave speed = distance/time
What is mega?
X106⃣ (represents to the power of 6)
What is kilo?
What is milli?
What is micro?
What is nano?
What type of wave is a sound wave?
A longitudinal wave.
What is wave direction parallel to?
The vibration that caused it.
What sound range can humans hears?
Between 20Hz and 20000Hz (20kHz).
How could you measure the speed of sound by making sound?
-Make a sound
-When it reaches microphone 1 the timer starts
-When sound passes microphone 2 timer stops
-Record the time repeat it then take the average
-Measure distance between microphones with a ruler
-work out with speed = distance/time
How could you measure the speed of sound with an echo?
-make a noise, start timer
-wait for echo to return, stop timer
-repeat, take average
-measure distance to wall (tape measure)
-use the equation speed = distance (x2)/time
X2 for echo there and back
What is the law of reflection?
The angle of incidence is equal to the angle of reflection
What is the angle i?
The angle of incidence measured between the normal and the ray.
What is the angle r?
The angle of reflection.
When does refraction occur?
When a wave bends.
When does refraction occur with water waves?
When the depth changes.
When does refraction occur with sound?
When temperature changes.
When light goes from a high n (refractive index) to a low n does the light bend towards the normal or away from the normal?
It bends away from the normal (and speeds up).
When light goes from a low n to a higher n does it bend towards or away from the normal?
It bends towards the normal (and slows down).
What should the n (refractive index) never be less than?
What is the refractive index of air?
What is the refractive index of water?
What is the refractive index of glass?
What Is the refractive index of diamond?
If the refractive index is bigger, what happens to the light?
It bends more (Snell's law).
State the refractive index (n) equation and rearrange it.
n = sin i/sin r
i = sin-1 (n x sin r)
r= sin-1 (sin i/n)
Find n if i = 35 degrees and r = 25 degrees.
n = sin i/sin r
n = sin(35)/sin(25) = 1.4
Find i if n = 1.5 and r = 33 degrees.
n = sin i/sin r
i = sin-1 (sin i x n)
i = sin-1 (sin 33 x 1.5) = 54.8 degrees
Find r if n = 2.4 and i = 18 degrees.
n = sin i/sin r
r = sin-1 (sin i/n)
r = sin-1 (sin18/2.4) = 7.4 degrees
When a block is in water, refraction occurs, how does the block appear.
It appears to be higher than it really is.
Dispersion: what does a prism do?
It splits white light into a colour spectrum.
Different wavelengths of light react...
By different amounts.
Which colour ha the longest wavelength?
Which colour refracts the least when passed through a triangular prism?
Which colour has the shortest wavelength?
Violet (400mm) (and it refracts more)
When will a ray be completely reflected?
When the angle of incidence is greater than a certain value.
What is the critical angle for glass?
What is the critical angle for diamond?
The criteria for total internal reflection?
The angle is greater than the critical angle.
When the light ray is travelling in a dense medium towards a less dense medium does theology bend towards or away from the normal?
Away from the normal.
What is the equation linking refractive index and the critical angle. Rearrange it.
n = 1/sin c
sin c = 1/n
c = sin-1 (1/n)
Find optic cable:
What does it contain?
A thin high n glass core surrounded by a slightly lower n glass shroud
What is diffraction?
The spreading out of waves.
The bending or spreading of a wave as it passes around the edge or passes through the gap.
What is the electromagnetic spectrum?
A group of waves which share certain properties.
What properties do electromagnetic waves share?
-They all can travel through a vacuum
-They all travel at the same speed which is the speed of light (3x108⃣ m/s)
-They are all transverse waves
-They all transfer energy
What are the electromagnetic waves?
Radio Long Low Low
Micro Wavelength f Energy
Visible ⬇️ ⬇️ ⬇️
Gamma. Short High High
What are the uses of radio waves?
What are the uses of micro waves?
What are the uses of infrared waves?
What are the uses of visible waves?
What are the uses of ultraviolet waves?
What are the uses of X-ray waves?
Imaging internal structures of the body and other objects
Studying atomic structure of metals
What are the uses of gamma rays?
Kill bacteria in food
Sterilise medical equipment
What're the dangers of radio waves?
What are the dangers of micro waves?
Internal heating of body tissues
What are the dangers of infrared waves?
Causes burning of tissues
What are the dangers of visible waves?
Very bright light can damage eyes
What are the dangers of ultra violet waves?
Damage surface cells
What are the dangers of X-rays ?
Long term exposure can cause cancer
What are the dangers of gamma waves?
What value can analogue have?
Any value (ANYlogue)
What value has digital got? And what is digital called?
Digital is discreet and can have only two value (On or off)
What are examples of digital?
CDs store music using digital, there are pits (0) and bumps (1) .
What are examples of analogue?
LPG records/vinyl store music using analogue, the grooves on the surface can have any height.
What happens to noise signals when they are sent?
They become noisy (signals get distorted)
When analogue signals are amplified...
The noise is too.
How do you get a digital signal back to the original signal after it's got noisy?
They can be cleaned then amplified.
What is it called when lots of signals are sent at the same time but don't interfere with each other?
What is the rounding of data to pack more in called?
Quantisation and signals are less affected by it.