Waves and Light Flashcards
What is White Light?
White light from the Sun is a mixture of colours, each with a different frequency.
What can we do with a Prism?
You can use a prism to split (or disperse) white light into a spectrum of colours
Name the All the colours in the spectrum
low frequency to high frequency
red orange yellow green blue indigo violet
What does Disperse mean?
The splitting of white light to form the colour spectrum
Name the 3 colours our eyes can detect:
Red, Green and blue
How can we see more than 3 colours?
By combining the 3 colours ,We can perceive many different colours
Give an example for dispersion:
By mixing red light and green light, for example, we can see yellow
What happens if we mix all Red, Green and blue light?
If all three are mixed together we see white light
How do objects have different colours?
Objects absorb and reflect light differently. A lemon reflects yellow light, all the other colours are absorbed and so are not seen by our eyes.
What would happen if the light ray is travelling along the Normal
if a light ray travelling along the normal hits a mirror, it is reflected straight back the way it came. The reflection of light from a flat surface such as a mirror is called specular reflection – light meeting the surface in one direction is all reflected in one direction.
What is the speed of light waves in a vaccum?
_ ___
\ / | | | 8
/ | | |
\ | | |
_ / X | | ___| m/s
What are the Primary colours (for light)?
Red,green and blue
WHAT ARE THE SECONDARY COLOURS FOR LIGHT?
Yellow, Cyan , Magneta
Name 6 features of a camera
Converging lens Shutter Focal Point Focusing screw Aperture Photo sensitive surface
What does the converging lens do?
They refract light rays so they can meet at 1 point
What does the shutter do?
a device that allows light to pass for a determined period, exposing photographic film
What does the focal point do?
the point at which rays or waves meet after reflection or refraction
What does the Focusing screw do?
used to adjust the focus
What does the Aperture do?
Controls How much light enters the camera
What does the Photo sensitive surface do?
Substance that changes in some way when it absorbs light, for example leading to a chemical or electrical change.
How did an Old fashioned Cameras produce an image?
In an old-fashioned camera, the photo-sensitive material was camera film. When the film absorbed light, a chemical change produced an image in the film, called the ‘negative’. This was used to produce a photograph on photo-sensitive paper.
How does a modern Camera Produce an Image?
In a modern camera or the camera in a mobile phone, the photo-sensitive material produces electrical impulses, which are used to produce an image file. This can be viewed on the screen, or its information sent to a printer
WHAT ARE THE 6 FEATURES OF THE EYE?
Iris Pupil Retina Optic nerve Lens Cornea
Iris=
The iris controls the amount of light that enters the eye by opening and closing the pupil.
Pupil=
controlling the amount of light entering the eye
Retina=
receive light that the lens has focused, convert the light into neural signals
Optic nerve=
to transfer visual information from the retina in your eye to the visual centers of your brain in the form of impulses, allowing your brain to translate these impulses as images in your head.
Lens=
along with the cornea, helps to refract light to be focused on the retina.
Explain One Way Superposition can be Demonstrated:
A ripple tank is a tank full of water in which a vibrating needle produces a stream of ripples. We can watch superposition and reflection in the water waves.
How do our Ears Detect Sound
An ear has an eardrum inside, connected to three small bones. The vibrations in the air make the eardrum vibrate, and these vibrations are passed through the three small bones (called ossicles) to a spiral structure called the cochlea. Signals are passed from the cochlea to the brain through the auditory nerve, and our brain interprets these signals as sound.
How does a Microphone Work?
Microphones contain a diaphragm, which does a similar job to an ear drum. The vibrations in air make the diaphragm vibrate, and these vibrations are changed to electrical impulses. In the lab, the electrical impulses can be sent to an oscilloscope, which represents them as a graph on a screen.
the greater the amplitude,
the louder the sound
the closer together the waves are and
the higher the pitch
Explain how the Clap-echo method works:
This method involves measuring the time taken for you to hear an echo from a sharp clap. You stand a long distance from a wall, clap, and listen for the echo. The distance travelled is twice the distance from you to the wall (because the sound has to travel to the wall and back
Name the 8 features of an ear
Pinna Ear Canal Eardrum Hammer Anvil Stirrup Cochlea Auditory Nerve
What is the Microphone?
The microphone is a device that converts sound waves into electrical signals.
Examples of longitudinal waves include:
sound waves
ultrasound waves
seismic P-waves
How are Sound Waves Detected?
by Diaphragms in Microphones
The vibrations in a sound wave make a sensitive diaphragm vibrate inside the microphones . The microphones convert the vibrations to electrical signals .
Don’t NEED TO KNOW BUT
Another device can record the electrical signals so that the sound can be reproduced later
TRANSVERSE WAVES=
OSCILLATIONS ARE PERPENDICULAR TO THE DIRECTION OF WENERGY TRANSFER
LONGITUDINAL WAVES=
OSCILLATIONS THAT ARE PARALELL TO THE DIRECTION OF ENERGY TRANSFER
High freq=
low freq=
Increase the current=
High freq= higher pitch sound
low freq= lower pitch sound
Increase the current= increase the amplitude of the vibration= increases the volume of the sound
5 steps of Hearing:
Objects Vibrate
Air vibrates
Ear Drum vibrates
Ear bones vibrate
Hairs vibrate in the cochlea, sending a message to the brain (along the auditory nerve)
What is a medium
Any substance that light or any other wave travels through is called a medium
Why will sometimes when light enters a glass block (for eg) , the direction of light will not change?
Because the light rays enters the glass block travelling straight on/along the normal
Why do rough surfaces look dull?
Because the light is reflected back in lots of different directions (scattered). This is diffuse reflection/diffuse scattering
What is Dispersion?
Spreading out of the different wavelengths of light, caused by refraction of light as it passes through a prism
Why can White objects appear different colours than white in filter and coloured light?
Because white objects reflect all colours
Explain why removing air makes sound STOP
Sound can’t travel in a vacuum as there no particles to pass on the vibrations
Name 2 equations that can find the speed/wave speed
wave speed (m/s) = frequency (Hz) × wavelength (m)
speed(m/s) =Distance (m) ÷ Time(s).
Remember to convert
Name the equation that can solve the distance
distance= speed x time
Remember that an echo is divided by 2
Ok
Cornea=
The cornea is the transparent part of the eye that covers the front portion of the eye. It covers the pupil ,iris .The cornea’s function is to refract light. The cornea is responsible for focusing most of the light .
What do Loudspeakers do?
Loudspeakers recreate sound wave
An electrical signal is fed into a loudspeaker. The signal causes the diaphragm to vibrate. This makes the air vibrate, producing sound waves. (microphone in reverse)
Name 3 examples of diaphragms
a thin paper or a plastic sheet or aluminium
Explain why Humans cant hear Ultrasound
Ultrasound waves have a higher pitch/frequency than the normal auditory range of humans
What can White light do?
White light can be split up into a spectrum of colours using a prism, a triangular block of glass or Perspex
Light is refracted when it enters the prism, and each colour is refracted by a different amount. This means that light leaving a prism is spread out into its different colours
How do you find out frequency ? NTK
Frequency/Hz = number of waves divide by time/s
