Light and Vision Flashcards
Are light waves transverse or longitudinal?
Transverse
What is the wavelength of a light wave?
The distance between two successive crests or troughs
What is frequency of a wave?
The number of complete waves that pass a point in one second
What is the velocity of a light wave? What is it dependant on?
How fast the wave is moving (depends on the medium it’s moving through)
What is the speed of light in a vacuum?
299,800km/s (8 times around the world in one second)
What is the range of wavelengths for radio waves?
1,000km-1mm
How does magnetic resonance imaging work?
Hydrogen atoms absorb and emit radio waves in a magnetic field, and the changing in atom alignment creates images of the body
What is the range of wavelengths for microwaves?
10cm-0.01cm
What is the range of wavelengths for visible light?
700nm-400nm
What are the types of UV light?
UVA, UVB, UVC
What type of UV light is largely responsible for sunburn and eventual skin cancer?
UVB
What type of UV light is mostly blocked by earth’s atmosphere and is the highest energy, most harmful to life type?
UVC
What type of UV light is the lowest energy yet can still cause skin damage?
UVA
How are X-Rays used to produce an X-Ray image?
An X-ray machine produces a concentrated beam of electrons which comes into contact with our body tissues and produces an image on a metal film
What is the most energetic form of light/electromagnetic wave?
Gamma Radiation/Rays
What are some medical uses for Gamma Radiation?
Sterilising medical equipment and Attacking cancer cells (in certain radio therapies)
What is light reflection?
Light bouncing off a surface at the same angle it hits the surface at
How is colour percieved?
When light is reflected off of certain objects, it is perceived as colour depending on the wavelength of light reflected
What is light refraction?
The changing of speed and trajectory of light as it moves from one medium to another
If light enters a denser medium, does it refract towards or away from the normal?
Towards the normal
If light enters a less dense medium, does it refract towards or away from the normal?
Away from the normal
What is the difference between polarised and unpolarised light?
Unpolarised light has electromagnetic fields oscillating in all possible directions, whereas polarised light has electromagnetic fields oscillating in only one direction
What is the front dome of the eye called?
The cornea
What is the “white” of the eye?
The sclera
What is the clear tissue over the sclera?
The conjunctiva
What is the liquid between the iris and the cornea?
The aqueous humour
Which part of the eye changes shape to focus incoming light onto the retina?
The lens
The eye behind the lens is filled with what? What is the difference in this substance between younger and older individuals?
Filled with the vitreous humour, which is more jelly-like at younger ages and more liquid-like in older individuals
Which part of the eye contains light receptive cells?
The retina
What layer is located between the sclera and the retina and supplies blood to the retina?
The choroid
What transmits the signals from the retina to the brain?
The optic nerve
What is the term for long-sightedness? Are people with long-sightedness better at seeing near or distant objects?
Hyperopia
People with hyperopia are better at seeing distant objects, while near objects appear blurry or cause eye strain
Where is the focal point of incoming light focused in hyperopic eyes? What type of lenses are used to correct this?
Behind the retina due to a short axial (front to back) left. Convex (+ve power) lenses are used to pull the focal point towards the front of the eye to focus it on the retina
What is the term for short-sightedness? Are people with short-sightedness better at seeing near or distant objects?
Myopia
People with myopia are better at seeing close objects, while distant objects appear blurry or cause eye strain
Where is the focal point of incoming light focused in myopic eyes? What type of lenses are used to correct this?
In front of the retina to a long axial (front to back) length. Concave (-ve power) lenses are used to push the focal point towards the back of the eye to focus it on the retina
What are some different types of blindness
Corneal opacity (translucency of the cornea caused by trauma, infection or disease) Cataract (Lens opacity caused by ageing or trauma) Retinal detachment (Separation of the retinal layer from the choroid) Visual Tract (Problems with transmission of signal through the optic nerve)
What is the purpose of the pinhole test?
Looking through a pinhole removes peripheral beams of light, which should improve hyperopic or myopic issues with the eye. If it doesn’t improve, it could be a neural issue.
