Energy can be transferred as both a particle and a wave.
4. Ways of Sensing
When we think of blindness we often think of not being able to see anything at all. Total vision loss is only one kind of blindness, but most blind people can detect some light. For this reason the term blindness is not quite right. Low vision may be a better description for people who are able to detect light but whose vision is impaired.
Many things can cause blindness and low vision. Most common are birth defects, injuries, and disease.
When you focus on something, the area to either side of what you’re focusing on is called the periphery and being able to see that is called peripheral vision. In one type of low vision, a person can only see what is directly ahead of them but nothing to the side (no peripheral vision). If you get an empty paper towel roll, hold it up to your eye, and look through it, you can simulate a type of low vision called tunnel vision.
Another type of low vision is the exact opposite of this. A person may have peripheral vision, but be unable to see what’s directly ahead.
Diabetes can sometimes cause vision loss, and some diabetics may become legally blind. With this type of blindness, the retina changes its sensitivity to light, creating many blind spots or areas where the cones and rods do not work well.
Colour blindness is not a form of blindness. It is a deficiency in the way you see colour. A person with this vision problem may have difficulty distinguishing certain colours. This is a hereditary condition, which means it is genetic and a person is born with it.
Colour blindness is caused by a defect in the cone cells in the retina that causes the loss of colour detection. There is no treatment it. For some people, tinted lenses and contact lenses can be used to help with colour perception but normal colour vision is never achieved.
This is a non-permanent, painful condition caused by overexposure to the glare of sunlight reflecting off snow, causing the cornea to become inflamed.
The Inuit of northern Canada carved goggles from caribou antlers to prevent snow blindness. The antler would be curved to fit the shape of the face, with a groove cut out for the nose and eye-slits carved to reduce the amount of light that entered the eye. The goggles were held in place with caribou sinew.
Welder’s flash is a condition similar to snow blindness, caused by not wearing a proper helmet when welding.