Eye-HOTS Flashcards
why does chicken go to sleep when its sunset
A chicken has only a few rod cells, so it can only respond to a bright light. When the sun sets, it cannot sense dim light so it goes to sleep.
we feel glared when we go from a dark room to a bright sunlight. why? also explain why we totally dark when we wnter a cinema hall
i) when we are in bright sunlight, the pupil gets constricted. since there is a maximum instensity of light, the pupil allows minimum amount of light to enter.
ii) when we are in a dark room, our pupil gets dilated. when there is low intensity of light, the pupil allows maximum amount of light to enter.
iii) so when we enter the cinema hall from the bright sun, the pupil has to go from constricted to dilated state. This takes some time. So the room looks completely dark from sometime.
iv) When we are in the cinema there is low intensity of light, so our pupils are dilated. When we enter the bright room a lot of bright light enters our eye and gives a glared feeling before the pupil becomes constricted
the least distance of distinct vision is 25cm. why is tht so ?
this is because the eye lens cannot decrease its focal length beyond a certain limit which is 25cm, the least distance of distinct vision.
why cant the eye see clearly the object palced less than 25cm from the eye.
the ciliray muscles cannot decrease the focal length of the eye lens beyond a certain limit.
what happens to image distance in the eye when we increase the object distance?
the object distance ( distance between the eye lens and the retina) remains constant. Rather the focal length of the eyes changes with respect to object dustance
why cat/bat can see clearly at night
tthe cat and bat have a large no of rod cells in their retina which allows them to see even with less intensity of light
why doesnt a myopic person use glasses when readin newspaper
i)myopic person has a normal near point ,ie 25cm. He has no strain in reading a newspaper at 25cm
ii) the myopic person has farpoint lesser than infinity. So hee needs concave lenses to correct his vision at long distance
what is persistence of vision
perisistence of vision means that the image of formed on our retina persists there for 1/16th of a second. It is used in cinematography
what causes colourblindess
colourblind people lack a few pigments in cone cells (generally blue/green)
what are the advantages of having 2 eyes
there are several advantages to having 2 eyes. It gives us a wider filed of view, huamn being has ahorixontal filed of view of 150 degress with one eye and 180 degrees with both eyes. the ability to detect faint objects is also more enhanced with two detectors than one
why do prey animals have eys on both sides of head
some animals usually pray animals have eyes on both sides of head to give the widest filed of view.
why are our two eyes posiitoned in the front
they are positioned in the front in favour of stereopsis. It is the perception of depth by our eyes,Since our eyes are seperated by a few cms, each eye sees a slightly different image. Our brain combines the both inages together and uses extra info to tell us how close or far the obj is.
what are the conditions necessary to donate eyes
-eye donors can belong to any age group and sex. people who used to wear spectacles or thosee operated for cataract can donate eyes. Those with diabetes,hypertension and asthma and those without communicable diseases can also donate eyes.
-the eyes must be dontated 4-6hours after death.
who cannot donate eyes
persons who were infected with or died because of aids, hepatitis b or c, rabies,acute leukaemia, tetanus,cholera, meningitis or encephalitis cannot donate eyes.
what does eye bacnk do
an eye bank collects, evaluates and distrubutes donated eyes, The donated eyes are evaluated using strict medical standards.Those eyes which are not suitable for transplantation are used for valuable research and medical education.
