Page 30 - Dream 2047 June 2020

ANNULAR S LAR ECLIPSE
PRECAUTIONS
The effects of solar retinopathy on the eye
(Source: Sue Ford/Science Photo Library)
means energy incident at retina
= 4 × 0.70 × 10-6 kw/cm2
= 3×10-6kw
The diameter of the image being0.2 mm, the energy absorbed in the retina concentrated in an area of 0.03 mm2will be equal to 0.03 × 10-2cm2 = 3 × 10-4 cm2.
Hence the concentration of solar energy (heat and light) in the area of the image will be equal to 3 × 10-6/3 × 10-4 = 10-2 kw/cm2or 100 kw/m2. This is about 74 times the solar energy incident on Earth per square metre (1.36 kw/m2). So, it is no wonder that it can cause retinal burns even if viewed for only a few seconds!
We all know how sunlight can start a fire when focussed through a magnifying glass. The Sun can do the same thing to your retina. Sometimes, following subliminal exposure, only temporary symptoms appear. But following severe exposure, a destructive burn may cause permanent damage, which is a serious matter when the macula is involved. A solar chorioretinal burn (sun blindness or photoretinitis) is an injury of this type.
In most cases, nothing abnormal is noticed
immediately except for the dazzling sensation. However, a diffuse cloud is seen floating before the eyes shortly afterwards, usually associated with irritating after-images, photophobia (fear of light), and occasionally photopsia (light flashes), as well as chromatopsia (colour disturbance). After 24 hours, this diffuse cloud contracts into a dense scotoma (a blind spot or area of depressed vision) which may last for weeks or months or even permanently. Intense solar radiations can hurt or destroy the retina rod and cone cells causing damage to your inner eye. So, do not take chances. Rush to an ophthalmologist in case of any symptoms mentioned earlier.
Observe solar eclipse safely
Do not attempt to observe the Sun directly, even during the partial (or annular) phases of any eclipse with the naked eye. Unless appropriate
filters are used, it may result in permanent eye damage or even blindness! It is, therefore, advisable to follow certain guidelines for safe viewing of a solar eclipse (partial or annular). The fact that the Sun appears darker in a filter such as smoked glass, sunglasses, coloured film, photographic neutral density filters, etc., it does not guarantee that your eyes would be safe. Damage to the eyes comes predominantly from invisible infrared wavelengths. Avoid all unnecessary risks.
Dr K.B. Bhushan is Scientist ‘D’ in Vigyan Prasar. Email: bhushan@vigyanprasar.gov.in
Looking at the Sun during eclipse hurts your eyes.
(Source: https://www.webmd.com/eye-health/news/20170809/during-eclipse-your-eye-can-scorch)
30 dream2047/june2020