Because light scattering does not occur outside the earth's atmosphere, an astronaut sees the sky as dark rather than blue.
Why does the sky appear dark instead of blue to an astronaut?
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The Human Eyes And The Colourful World
Why does the Sun appear reddish early in the morning?
Before reaching the observer, white light from the sun must travel a greater distance through the atmosphere. During this time, all coloured lights scatter save the light that corresponds to the red...
Explain why the planets do not twinkle?
Planets, unlike stars, do not sparkle. Stars are so far away that they appear in the night sky as pinpoints of light, even when viewed through a telescope. Because all of the light comes from a...
Why do stars twinkle?
The refraction of starlight being done by the atmosphere causes the twinkling of a star. When starlight enters the earth's atmosphere, it undergoes constant refraction before reaching the surface....
What happens to the image distance in the eye when we increase the distance of an object from the eye?
Even when an object is moved further away from the eye, an image is produced on the retina. As the object is pushed away from the eye, the eye lens grows smaller and the focus length rises.
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
Because the ciliary muscles of the eyes are unable to contract beyond a certain limit, a typical eye cannot perceive objects closer than 25 cm clearly.
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.
Hypermetropia allows a person to see different items well, but also makes it difficult to perceive objects in close proximity. Because the eye lens focuses the incoming divergent rays beyond the...
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Myopia is a condition that affects the individual. The image is created in front of the retina in this condition. As a result, a concave lens is utilized to treat this eyesight problem. Object...
A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?
The relation between the power and focal length is given by: Power (P) = 1/f (i) Power of the lens (used for correcting distant vision) as given is – 5.5 D Focal length of the lens (f) will...
The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
(c) 25 cm For a young adult with normal vision, the minimum distance of clear vision is 25 cm.
The human eye forms an image of an object at its
(a) cornea
(b) iris
(c) pupil
(d) retina
(d) retina The retina is a layer of nerve cells that lines the interior of the eye's rear wall. This layer detects light and transmits information to the brain, allowing you to see.
The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
(a) presbyopia
(b) accommodation
(c) near-sightedness
(d) far-sightedness
(b) accommodation The human eye can adapt the focal length of the eye lens to focus things at different distances because of accommodation.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
Short-sightedness, often known as myopia, affects the student. Myopia can be rectified with the use of a power-appropriate concave or divergent lens.
What is the far point and near point of the human eye with normal vision?
The near point of the eye is the shortest distance between an object and the eye at which it may be viewed clearly without strain. This distance is 25 cm for a regular person's eye. The far point of...
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of corrective lens used to restore proper vision?
To restore adequate vision, a person with a myopic eye should use a concave lens with a focal length of 1.2 m.
What is meant by power of accommodation of the eye?
Power of accommodation of eye means: The ability of the eye's lens to change its focal length to clearly concentrate rays from far away as well as close objects on the retina.
A person finds difficulty in seeing nearby objects clearly. His vision can be corrected by using spectacles containing:
a) converging lenses
b) diverging lenses
c) prismatic lenses
d) chromatic lenses
a) Converging lenses is the right answer.
A person cannot see distant objects clearly. His vision can be corrected by using the spectacles containing:
a) concave lenses
b) plane lenses
c) contact lenses
d) convex lenses
a) concave lenses is the right answer.
The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
a) myopia
b) presbyopia
c) colour blindness
d) cataract
d) cataract is the correct answer.
A man driving a car can read a distant road sign clearly but finds difficulty in reading the odometer on the dashboard of the car. Which of the following statement is correct about this man?
a) the near point of his eyes has receded away
b) the near point of his eyes has come closer to him
c) the far point of his eyes has receded away
d) the far point of his eyes has come closer to him
The correct answer is a) his eyes' near point has receded.
A student sitting on the last bench in the class cannot read the writing on the blackboard clearly but he can read the book lying on his desk clearly. Which of the following statement is correct about the student?
a) the near point of his eyes has receded away
b) the near point of his eyes has come closer to him
c) the far point of his eyes has receded away
d) the far point of his eyes has come closer to him
The correct answer is d) his eyes' distant point has moved closer to him
A person got his eyes tested. The optician’s prescription for the spectacles reads:
Left eye: -3.00D
Right eye: -3.50D
The person is having a defect of vision called:
a) presbyopia
b) myopia
c) astigmatism
d) hypermetropia
b) myopia is the proper answer.
After testing the eyes of a child, the optician has prescribed the following lenses for his spectacles:
Left eye: +2.00D
Right eye: +2.25D
The child is suffering from the defect of vision called:
a) short-sightedness
b) long-sightedness
c) cataract
d) presbyopia
Long-sightedness is the right answer.
A young man has to hold a book at arm’s length to be able to read it clearly. The defect of vision is:
a) astigmatism
b) myopia
c) presbyopia
d) hypermetropia
d) hypermetropia is the right answer.
Though a woman can see the distant objects clearly, she cannot see the nearby objects clearly. She is suffering from the defect of vision called:
a) long-sight
b) short-sight
c) hind-sight
d) mid-sight
a) long-sight is the right answer.
A person cannot see the distant objects clearly. He is suffering from the defect of vision called:
a) cataract
b) hypermetropia
c) myopia
d) presbyopia
c) myopia is the correct answer.
The defect of vision which cannot be corrected by using spectacles is:
a) myopia
b) presbyopia
c) cataract
d) hypermetropia
c) cataract is the correct answer.
The human eye can focus objects at focus objects at different distances by adjusting the focal length of the eye-lens. This is due to:
a) presbyopia
b) accommodation
c) near-sightedness
d) far-sightedness
Accommodation is the correct answer.
a) What is long-sightedness? State the two causes of long-sightedness. With the help of ray diagram, show:
i) the eye defect long sightedness
ii) correction of long-sightedness using a lens
b) An eye has a near point distance of 0.72m. What sort of lens in spectacles would be needed to reduce the near point distance to 0.25m? Also, calculate the power of lens required. Is this eye long-sighted or short-sighted?
c) An eye has far point of 2m. What type of lens in spectacles would be needed to increase the far point to infinity? Also, calculate the power of lens required. Is this eye long-sighted or short-sighted?
a) Long sightedness is a vision problem in which a person can't see items that are far away yet can see objects that are close by. The two main reasons of long-sightedness are as follows: I The eye...
a) What is short-sightedness? State the two causes of short-sightedness. With the help of ray diagram, show:
i) the eye defect short-sightedness
ii) correction of short-sightedness by using a lens
b) A person having short-sight cannot see objects clearly beyond a distance of 1.5m. What would be the nature and power of the corrective lens to restore proper vision?
a) Short sightedness is a vision problem in which a person has trouble seeing items that are maintained close by. The two main causes of nearsightedness are as follows: I An excessive curvature of...
Fill in the following blanks with suitable words:
A person is short-sighted if his eyeball is too …….. Spectacles with a ………… lens are needed. A person is long-sighted of his eyeball is too ……….. Spectacles with a …………. lens are needed. These focus light rays exactly on to the ………..
Long, concave, short, convex, and retina are some of the shapes available.
When is a person said to have developed cataract in his eye? How is the vision of a person having cataract restored?
When a person's eye develops a gradual hazy development that causes impaired vision, he is said to have acquired cataract. Surgery is used to address this flaw. In addition, an opaque lens is...
What is presbyopia? Write two causes of this defect. Name the type of lens which can be used to correct presbyopia.
Presbyopia is a visual problem in which a person's ability to perceive adjacent things is hampered owing to a lack of eye accommodation power. This is due to the ciliary muscles being weaker and the...
A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision, he needs a lens of power +1.5 dioptres. What is the focal length of the lens required for correcting
a) Distant vision
b) Near vision
a) For long-range vision, P = -5.5D 1/f = P f = 1/P = -18.18cm b) For close-up vision, 1.5D = P 1/f = P f = 1/P = 66.66cm
The near point of a person suffering from hypermetropia is at 50cm from his eye. What is the nature and power of the lens needed to correct this defect?
If you have hypermetropia, you should wear convex lenses. Given, u = -25cm object distance v = -50cm image distance 1/v-1/u=1/f 100/f = 100/50 = 2D
A person suffering from the eye defect myopia can see clearly only up to a distance of 2 metres. What is the nature and power of lens required to rectify this defect?
Myopia sufferers can benefit from concave lenses. Given, 2m is the far point of a myopic eye. u = infinite, object distance v = 2m image distance 1/v-1/u=1/f f = -2m f = -2m f = -2m -0.5D = P = 1/f...
Explain with the help of a labelled ray diagram, the defect of vision called hypermetropia and how it is corrected by a lens.
Hypermetropia, often known as long-sightedness, is a condition in which a person is unable to see clearly adjacent things. A convex lens can be used to remedy the problem. The ray diagram is as...
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
Myopia, often known as short-sightedness, is a condition in which a person has trouble seeing objects that are close by. A concave lens is used to remedy this flaw. The ray diagram for myopia...
Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defects.
Myopia is corrected using a diverging lens. The ray diagram for myopia correction is as follows: a) For a myopic eye, image production occurs in the front of the retina. b) F is the myopic eye's far...
Name the defect of vision which can be corrected by a converging lens. Show clearly by a ray diagram how the lens corrects the defect.
Hypermetropia is corrected using a convergent lens. a) If a person has hypermetropia, the image of a close object will develop behind the retina. b) N' is the hypermetropic eye's near point, which...
Differentiate between myopia and hypermetropia. What type of spectacles should be worn by a person having the defects of myopia as well as hypermetropia? How it help?
Myopia is a condition in which a person can see items close up but has trouble seeing objects at a distance. Hypermetropia is a condition in which a person can see items that are situated at a...
What are the two most common defects of vision? How are they corrected?
Myopia and hypermetropia are the two most frequent visual problems that may be treated by concave and convex lenses, respectively.
Complete the following sentences:
a) A short-sighted person cannot see ………. objects clearly. Short-sightedness can be corrected by using ……. lenses.
b) A long-sighted person cannot see ………… objects clearly. Long-sightedness can be corrected by using …….. lenses.
a) Distant, concave b) Nearby, convex
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
a) Name the type of defect he is suffering from.
b) How can this defect by corrected?
a) Myopia b) Concave lens
A man can read the number of a distant bus clearly but he finds difficulty in reading a book. A man can read the number of a distant bus clearly but he finds difficulty in reading a book.
a) From which defect of the eye is he suffering?
b) What type of spectacle lens should he use to correct the defect?
a) Hypermetropia b) Convex lens
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
a) Is she short-sighted or long-sighted?
b) What type of lenses: converging or diverging would an optician prescribe for her?
a) Short-sighted b) Diverging lenses
Where is the near point of a person suffering from hypermetropia?
The near point for a person with hypermetropia is 25 centimetres.
What is the far point of person suffering from myopia?
Less than infinity is the furthest point for a myopic person
Name the body part with which the terms myopia and hypermetropia are connected.
Eye
Name one defect of vision which cannot be corrected by any type of spectacle lenses.
Cataract
Name any two defects of vision which can be corrected by using spectacles.
a) Myopia b) Hypermetropia
What is the other name of old age hypermetropia?
Presbyopia
Name the defect of vision which makes the eye lens cloudy resulting in blurred vision.
Cataract is the visual impairment that causes the eye lens to become hazy, resulting in blurred vision.
Name the defect of vision in which the eye lens loses its power of accommodation due to old age
Presbyopia is the visual problem caused by the eye lens losing its accommodation power as it ages.
State whether the following statement is true or false:
Short-sightedness can be cured by using a concave lens.
A concave lens can be used to correct short-sightedness.
What kind of lens is used to correct
a) Short-sightedness
b) Long-sightedness
a) Concave lens b) Convex lens
What is the scientific name of
a) Short-sightedness
b) Long-sightedness
a) Myopia b) Hypermetropia
What is the other name for
a) Myopia
b) Hypermetropia
a) Near-sightedness b) Far-sightedness
What type of lens is used to correct
a) Hypermetropia
b) Myopia
a)convex lens are kind of corrective lens used. b)concave lens are kind of corrective lens used
Which defect of vision can be rectified:
a) By using a concave lens?
b) By using a convex lens?
a) Through the use of a concave lens-Myopia b) Through the use of a convex lens-Hypermetropia
Name the defect of vision in a person:
a) Whose near point is more than 25cm away.
b) Whose far point is less than infinity.
a) Whose nearest point is further away than 25cm is Hypermetropia b) Whose far point is smaller than the limit of infinity Myopia
Name one of the common defects of vision and the type of lens used to remove it.
Myopia is one of the visual impairments that may be corrected using a concave lens.
The size of the pupil of the eye is adjusted by:
a) cornea
b) ciliary muscles
c) optic nerve
d) iris
d) iris is the correct answer.
Which of the following changes occur when you walk out of bright sunshine into a poorly lit room?
a) the pupil becomes larger
b) the lens becomes thicker
c) the ciliary muscles relaxes
d) the pupil becomes smaller
The correct response is a) the pupil enlarges.
How does the eye change in order to focus on near or distant object?
a) the lens moves in or out
b) the retina moves in or out
c) the lens becomes thicker or thinner
d) the pupil gets larger or smaller
The correct response is c) the lens thickens or thins.
The human eye possesses the power of accommodation. This is the power to:
a) alter the diameter of the pupil as the intensity of light changes
b) distinguish between lights of different colours
c) focus on objects at different distances
d) decide which of the two objects is closer
The correct response is c) concentrate on things at various distances.
Which of the following controls the amount of light entering the eye?
a) ciliary muscles
b) lens
c) iris
d) cornea
c) iris is the correct answer.
The term “accommodation” as applied to the eye, refers to its ability to:
a) control the light intensity falling on the retina
b) erect the inverted image formed on the retina
c) vary the focal length of the lens
d) vary the distance between the lens and retina
The correct answer is c) change the lens' focal length.
To focus the image of a nearby object on the retina of an eye:
a) the distance between eye-lens and retina is increased
b) the distance between eye-lens and retina is decreased
c) the thickness of eye-lens is decreased
d) the thickness of eye-lens is increased
The correct response is d) the eye-lens thickness is raised.
Refraction of light in the eye occurs at:
a) the lens only
b) the cornea only
c) both the cornea and the lens
d) the pupil
The proper response is c), which includes both the cornea and the lens.
The least distance of distinct vision for a young adult with normal vision is about:
a) 25m
b) 2.5cm
c) 25cm
d) 2.5m
b) 25cm is the right answer.
The change in focal length of an eye-lens is caused by the action of the:
a) pupil
b) retina
c) ciliary muscles
d) iris
Ciliary muscles is the right answer.
The human eye forms the image of an object at its:
a) cornea
b) iris
c) pupil
d) retina
d) retina is the right answer.
a) Explain the functions of the following parts of the eye:
a) cornea
b) iris
c) pupil
d) ciliary muscles
e) eye-lens
f) retina
g) optic nerve
b) If you walk from a dark room into sunlight and back again into dark room, how would your pupils alter in size? What makes this happen?
c) Explain why we cannot see our seats first when we enter a darkened cinema hall from bright light but gradually they become visible.
a) Cornea: The cornea is the front portion of an eye through which light enters. b) Iris: The iris regulates the quantity of light that enters the eye. c) Pupil: The pupil controls the amount of...
a) Draw a simple diagram of the human eye and label clearly the cornea, iris, pupil, ciliary muscles, eye lens, retina, optic never, and blind spot.
b) Describe the working of the human eye with the help of the above diagram.
c) How does the eye adjust itself to deal with light of varying intensity?
b)working of human eye c)The iris changes the size of the pupil in response to changing light intensity. The iris contracts the pupil and decreases the quantity of light entering the eye when the...
a) What happens to the size of pupil of our eye
i) in dim light
ii) in bright light
b) Name the cells on the retina of an eye which are sensitive to
i) bright light?
ii) dim light
iii) sensation of colour
a) (i) In dim light, the pupil dilates. ii) In strong light, the pupil shrinks.' b) i) Cones ii) Rods iii) Cones
a) How does the convex eye lens differ from the ordinary convex lens made of glass?
b) List in order the parts of the eye through which light passes to reach the retina.
a) The convex eye lens differs from a regular convex lens in that the ciliary images regulate the focal length of the convex lens in the eye, but the focal length of a regular convex lens is set by...
What are rods and cones in the retina of an eye? Why is our night vision relatively poor compared t the night vision of an owl?
The cells in the retina of an eye are called rods and cones. Rods are cells that have a rod form and are sensitive to low light. Cones are light-sensitive cones that are cone-shaped. Humans have a...
There are two types of light-sensitive cells in the human eye:
a) Where are they found?
b) What is each type called?
c) To what is each type of cell sensitive?
a) The retina has two types of light-sensitive cells. b) Rods and cones are the names for these cells. c) Rods respond to dim light, whereas cones respond to strong light.
Describe and explain how a normal eye can see objects lying at various distances clearly.
The ciliary muscles are used to concentrate on objects that are far away. The suspensory ligaments are drawn and connected to the eye lens, and the ciliary muscles are totally relaxed.
Ciliary muscles of human eye can contract or relax. How does it help in the normal functioning of the eye?
When the ciliary muscle relaxes, the eye lens becomes thinner, making it easier to perceive distant things. When the ciliary muscle contracts, the eye lens thickens, making it easier to view close...
A person walking in a dark corridor enters into a brightly lit room:
a) State the effect on the pupil of the eye
b) How does this affect the amount of light entering the eye?
a) The pupil reduces in size. b) There is a reduction in the quantity of light that enters the eye.
Why does it take some time to see objects in a dim room when you enter the room from bright sunshine outside?
When you enter a dim room from bright sunlight outside, it takes some time to see items since the pupil size is tiny and the intensity of light outside is higher. The pupil widens as we enter a...
What happens to the eye when you enter a darkened cinema hall from bright sunshine? Give reason for your answer.
When we walk into a darkened cinema theatre after being in strong sunlight, we can't see much well at first. However, our vision improves quickly. Because the amount of light entering the eye...
How is the amount of light entering the eye controlled?
The quantity of light that enters the eye is controlled by the iris. The size of the pupil is changed depending on the strength of the light received by the eye. If the intensity of the light...
What change is made in the eye to enable it to focus on objects situated at different distances? Ilustrate your answer with the help of diagrams.
The ciliary muscles of the eye must either be totally relaxed or stretched in order for an eye to concentrate on things at varying distances. The ciliary muscle contracts, causing the suspensory...
The eyes of a person are focused
i) On a nearby object
ii) On a distant object, turn by turn. In which case:
a) The focal length of eye-lens will be the maximum?
b) The converging power of eye-lens will be the maximum?
a) When the eye is focused on a distant object, the focal length of the eye-lens is at its maximum. b) When the eye is focused on a close object, the converging power of the eye-lens is at its...
What changes take place in the shape of eye-lens:
a) When the eye is focused on a near object?
b) When the eye is focused on a distant object?
a) The eye-lens thickens when the eye is focused on a close object. b) The eye-lens grows narrower when the eye is focused on a distant object.
Why is a normal eye not able to see clearly the objects placed closer than 25cm?
Because the eye's accommodation power of 25cm is spent, a typical eye cannot see clearly things that are put closer than 25cm. When the eye's maximal accommodation is achieved, the ciliary muscles...
Fill in the following blanks with suitable words:
a) Most of the refraction of light rays entering the eye occurs at the outer surface of the ……
b) The part of eye sensitive to light is ……….
c) The part of eye which alters the size of the pupil is ………….
d) When light is dim, the pupil becomes ……………
e) The iris controls the amount of ……… entering the eye.
f) The ciliary muscles control the shape of the ………
g) To bring light from a distant object to a focus on the retina of the eye, the convex eye-lens needs to be made …….?
h) To bring light from a near object to a focus on the retina of the eye, the convex eye lens needs to be made …….
a) The outer surface of the eye is where the majority of light rays entering the eye are refracted is cornea, b) The light-sensitive portion of the eye is retina, c) The portion of the eye that...
Give the scientific names of the following parts of the eye:
a) Carries signals from an eye to the brain
b) Muscles which change the shape of the eye-lens
c) A hole in the middle of the iris
d) A clear window at the front of the eye
e) Changes shape to focus a picture on the retina
a) The optic nerve b) Muscles of the iliac crest c) Student d)Cornea e) Contact lenses
Define the term “power of accommodation” of human eye.
The capacity of an eye to concentrate a distant as well as a local object on the retina by altering the focal length of the lens is known as power of accommodation.
Name the part of our eyes which helps us to focus near and distant objects in quick succession.
Ciliary muscles allow us to focus on both close and far things in rapid succession.
What is the range of vision of a normal human eye?
A typical human eye has a visual range of infinity to 25cm.
What is the:
a) Far point of a normal human eye?
b) Near point of a normal human eye?
a) The furthest point of a typical human eye is infinity. b) The near point of a typical human eye is 25 cm.
What is the least distance of distinct vision for a normal human eye?
For a typical human eye, the minimum distance of clear vision is 25cm.
What do the ciliary muscles do when you are focusing on a nearby object?
The ciliary muscle thickens the lens of the eye as it focuses on a close object.
What changes the shape of lens in the eye?
The ciliary muscles serve to alter the shape of the lens in the eye.
Where does the greatest degree of refraction of light occur in the eye?
The cornea of the eye has the highest degree of refraction of light
What is the principal function of the eye-lens?
The eye-lens' main job is to concentrate light on the retina.
State whether the following statement is true or false:
The image formed on our retina is upside-down.
The given statement is true.
Out of rods and cones in the retina of your eye:
a) Which detect colour?
b) Which work in dim light?
a) Cones is the answer b) Rods is the answer
Name two types of cells in the retina of an eye which respond to light.
The two types of light-responsive cells in the retina of an eye are rods and cones.
Which part of the eye contains cells which are sensitive to light?
Light-sensitive cells can be found in the retina.
Name the part of the retina which is insensitive to light.
A blind spot is an area of the retina that is unresponsive to light.
Name that part of the eye which is equivalent to the photographic film in a camera.
The retina is the portion of the eye that functions similarly to photographic film in a camera.
Flow does the eye adjust to take account of an increase in brightness?
This is accomplished by contracting the pupil of our eyes.
What job does the pupil of the eye do?
The pupil in the eye's duty is to enlarge or shrink in response to the intensity of light surrounding it.
What is the function of the lens in the human eye?
The purpose of an eye lens is to alter the shape and thickness of light so that it can concentrate on the retina.
Where is the image formed in a human eye?
The retina of the human eye is where a picture is generated.
What is the name of
a) The curved, transparent front surface of the eye?
b) The light-sensitive layer in the eye?
a) Cornea is the answer b) Retina is the answer
Name the part of eye:
a) Which controls the amount of light entering the eye
b) On which the image is formed
c) Which changes the focal length of eye-lens
a) Iris is the answer b) Retina is the answer c) Ciliary muscles is the answer
Name two parts of the eye which refract light rays.
The cornea and eye-lens are the two components of the eye that refract light rays.
What kind of lens is present in the human eye?
The human eye contains a convex lens.