Light and sound Flashcards
Light is a wave which always travels in …..
A straight line
Which travels faster light or sound?
Light
Give an example which demonstrates that light travels faster than sound
In a race you see the smoke from the starting pistol before you hear the bang.
Whereabouts does light travel fastest?
In a vacuum
State the speed of light.
3 x 108
How long does it take the light from the sun to reach the Earth?
8.3 minutes
What is a vacuum
A space which contains nothing - no particles at all even air
Space is a vacuum
Nothing travels faster than what in a vacuum?
ilght
What happens when light hits a prism?
The white light splits into the light spectrum
State the colours of the light spectrum in the order they come out of a prism
Red
Orange
Yellow
Green
Blue
Indigo
Violet
What do we see when light from the sun hits raindrops
A rainbow
What causes a rainbow?
Light from the sun hits drops of rain, the light splits into the light spectrum.
State another name for a light wave
A light ray
Explain how we see objects
A light source is needed which can be sunlight or artificial light
The light is reflected off non luminous objects such as people or furniture
Some of that reflected light goes into our eyes allowing us to see
What is a mirror?
An object with a smooth shiny surface which reflects light.
What is a plane mirror
A mirror which is flat and reflects light back at the same angle giving a clear reflection
State the law of reflection
Angle of incidence = Angle of reflection
Angle i = Angle r
What is this a picture showing?
The law of reflection in a plane mirror
Give 2 practical examples of mirrors used in transport
- The rearview mirror on a car allows the driver to see vehicles behind them
- A mirror on a sharp bend or concealed entrance can allow a driver to see what is coming.
Explain how a periscope uses mirrors to allow you to see around a corner.
A tube contains two mirrors each set at 45 degrees. The light reflects from one mirror to the other and into the eye
What is refraction
It is where light bends as it crosses a boundary between different substances
What is a transparent material?
Something which light can travel through
What is an opaque material?
Something which light cannot travel through
What is a medium?
It is something that waves can travel through eg light waves or sound waves
If light hits a medium at an angle. How does the light bend when it travels from a less dense medium to a more dense medium?
Eg from air into glass
It bends towards the normal
The normal is perpendicular to the two mediums (90 degrees)
If light hits a medium at an angle. How does the light bend when it travels from a more dense medium to a less dense medium?
eg from glass to air
It bends away from the normal
The normal is perpendicular to the two mediums (90 degrees)
If light hits a different medium in a straight line does it bend or travel through in a straight line
A straight line
Why does sound need a medium to travel through?
It needs something to pass on the sound vibrations?
Can you hear sound in a vacuum?
NO because sound needs something to pass on the sound vibrations?
Describe the bell jar demo for sound
A bell is put in a bell jar which is attached to a vacuum pump
Whilst there is air in the jar the bell can be heard ringing because the air vibrates and the sound waves can travel to our ears
As the air is sucked out of the jar there is no air to vibrate so the sound cannot be heard.
What does an oscilloscope show
The amplitude and frequency of a sound wave
What is the amplitude of a wave?
It is the height of the wave
It shows the amount of energy the wave has
The higher the amplitude the louder the sound
What is the frequency of a wave?
It is the number of waves which pass a point in one second
High frequency gives a high pitched note
Lower frequency notes are lower pitch
How do we hear sounds?
What is the name of the nerve which carries messages to the brain from the cochlea?
Auditory nerve
What is audible range?
It is the range of frequencies you can hear
What is the average audible range for humans?
20 to 20,000 Hertz (Hz)
What is frequency measured in?
Hertz (Hz)
What is loudness measured in?
decibels (dB)
State some possible causes of poor hearing
- wax blocking ears
- nerve damage
- damage caused by illness or injury
- old age
Hearing can be damaged by sounds above……
85 dB
Sudden loud noises such as explosions can cause what sort of damage to the ears?
- Burst the ear drum
- Damage the ear bones
How can loud noises for extended periods of time can damage the ears
They damage the hairs in the cochlea
