Light & Sound Flashcards
What is luminous?
Something that gives off its own light energy
What is illuminous?
Doesn’t give off its own light energy - reflects light etc
Describe light
Travels as beams or rays in straight lines. It travels much faster that sound
How do we see things?
Light bounces off objects into our eyes (the retina)
What are the similarities of sound and light?
They both travel in a type of wave. They can both reflect and bounce off objects
What are the differences between sound and light?
Light travels much faster. Sound isn’t visible. Light doesn’t need particles to travel through
How do we know that light waves don’t need particles to travel through?
We can see the Suns light down on earth (no particles in space)
What does transparent mean?
Light is transmitted. You can see through it
What does translucent mean?
Some light is transmitted
What does opaque mean?
Light is absorbed or reflected. No light is transmitted
What does reflected mean?
Light is bounced off this object??
What does absorbed mean?
Light is “taken in”?
What does transmitted mean?
Light can go through it
What does a shadow represent?
The absence of light
What does every opaque object leave behind them?
A shadow, opposite to the direction of light
What is a regular reflection?
When light rays bounce off a smooth surface in parallel lines. The light is not scattered
What is diffuse reflection?
Light rays bounce off rough surfaces in scattered directions
What are the different parts of reflection?
Incident ray, reflected ray, angle of incidence, angle of reflection, normal
What is the normal?
An imaginary line 90° form the mirror
What is the rule of reflection?
Angle of incidence = angle of reflection
How do we measure the angle of incidence/reflection?
From the incident/reflected ray to the normal
What is a medium?
The material light travel through
What is refraction
When the speed light travels at changes through different densities
Which way do rays bend when it slows down?
It bends towards the normal
Which way do rays bend through a less dense medium? (Speeds up)
Away from the normal
Why does a ray of light bend in a denser medium (how)
Part of the wave hits the dense object first and slows down before the other part.
What is dispersion?
When white light is split up into its seven colours of the spectrum
What are the colours of the spectrum?
Red, orange, yellow, green, blue, indigo, violet
How are the colours split?
The different colours have different wave lengths. So they refract before each other making them disperse
What type of wave is light?
Electromagnetic, transverse
What are the primary colours of light?
Red, blue, green (they are all single waves)
What does green and blue lights make?
Cyan
What does red and blue lights make?
Magenta
What does green and red lights make?
Yellow (Amber)
How do we see red objects in white light?
All the colours in the spectrum get absorbed apart from red which is reflected into our eyes
What would a red object look like in blue light?
It would look black since the red object absorbs blue light as its a single wave and doesn’t reflect any other colours
What colour does a blue object look in white light?
Blue - all the colours are absorbed but blue is reflected
What colour does a blue object look in red light?
Black - blue is absorbed and none is reflected
What colour does a blue object look in magenta light?
Blue - magenta is red and blue light so it absorbs the red and reflects the blue
How are sounds made?
Vibrations
What is the first stage of audible hearing?
Sound waves channel through the auditory canal and hit the eardrum
What is the second stage of audible hearing?
Vibrations of the eardrum pass onto tiny bones called ossicles in the middle ear
What is the third stage of audible hearing?
The ossicles transmit the vibrations to the cochlea in the inner ear
What is the fourth stage of audible hearing?
Tiny hair cells in the cochlea help transmit electrical signals through the auditory nerve to the brain
What are the different parts of the ear?
Pinna, auditory canal, eardrum, ossicles, cochlea, auditory nerve
What does the pinna do?
It’s big surface “collect” sound waves
What is ultrasound?
Very high pitched noises. They are so high humans can’t hear them
What is infrasound?
Very low pitched noises. They are so low humans can’t hear them
What animals use ultrasound?
Bats, dogs and dolphins.
What is echo-locating?
When sound waves bounce off an object and animals know how far away it is
What animals use infrasound?
Elephants and giraffes
What is the frequency of sound?
The number of vibrations per second. It is measured in Hertz (Hz). Higher pitched sounds have higher frequencies
What is amplitude?
The distance between the midpoint and the furthest point. Louder sounds have higher amplitudes
What does a CRO show?
The pattern of sounds on a screen
What is a kilo hertz equivalent to?
1000 hertz
How does sound travel?
Sound travels as particles. They vibrate but don’t move. They simply bang into each other and compress.
What does the sound wave show about the particles?
The compression in particles vibrating in the ear. In between the compression is rarefaction
What type of waves are sound waves?
Longitude
Can sound travel through a vacuum?
No - only solids, gases and liquids
What do you look at in a sound wave to find out the volume?
The amplitude - the higher the amplitude the louder the sound
What do you look at in a sound wave to find the pitch
Frequency - the more waves per second, the higher the pitch
What state of matter does sound travel best in?
Solid - because the particles are closer together so energy can be passed on quicker
Then liquid then gas
Why can’t sound travel in a vacuum?
Because sound needs particles to travel
Why is gas the slowest state for sound to travel through?
Because the particles are more spread out and move in random directions, it is harder for the sound vibrations to pass into each other.
What is wavelength?
The difference between 2 crests
What is distance in a sound wave?
The width of a crest or trough (from the midpoint)
What is a crest in a sound wave?
The bit of the wave above the midpoint
What is a trough in a sound wave?
The bit of the wave under the midpoint
How do we hear a guitar? (Using particles)
When we pluck a string, it vibrates and causes the particles around it to vibrate with the same frequencies, passing them onto each other causing compressions and rarefactions until it reaches our ears
What is the loudness of sound measured in?
Decibels dB
The louder the sound the _____ energy
More
If the decibel number is 10 more than another number it is…
Twice as loud
What makes us loose our hearing as we get older?
The small hairs in the cochlea get damaged and don’t repair
As you get fitter, your heart rate gets ________ and your your recovery time is _________. Why?
Slower, quicker. Because the heart is stronger and can pump more blood to get more energy
How can we stop sound from echoing/reflecting?
Using carpets or curtains to absorb the energy since smooth surfaces are good at reflecting sound
How can we prevent our ears being damaged in future?
By keeping away from loud noises, wearing earplugs, putting music on low volume
