All Exams >
Class 10 >
Science and Technology Class 10 (Maharashtra SSC Board) >
All Questions
All questions of Lenses for Class 10 Exam
We use __________ lens to correct Hypermetropia- a)Biconvex
- b)Biconcave
- c)Concave
- d)Convex
Correct answer is option 'D'. Can you explain this answer?
We use __________ lens to correct Hypermetropia
a)
Biconvex
b)
Biconcave
c)
Concave
d)
Convex
|
Anjali Kapoor answered |
Concave lenses are used here. They spread the light out before it reaches the convex lens in the eye, therefore letting the image focus directly on the retina. Hyperopia is known to you probably as farsightedness.
Can you explain the answer of this question below:A concave lens of 20 cm focal length forms an image 15 cm from the lens. What is the object distance?
- A:
60 cm
- B:
30 cm
- C:
-60 cm
- D:
-30 cm
The answer is c.
A concave lens of 20 cm focal length forms an image 15 cm from the lens. What is the object distance?
60 cm
30 cm
-60 cm
-30 cm
|
Pooja Shah answered |
Focal length= -20(as it is concave lens)
v= -15 (as concave lens always forms virtual and erect image on left of lens)
Putting these values in lens formula,
1/ -20 - 1/u = 1/ -15
-1/ u= 1/-15 + 1/20
-1/u = -4+3/60
-1/u = -1/60
-u = -60
[u =60]
v= -15 (as concave lens always forms virtual and erect image on left of lens)
Putting these values in lens formula,
1/ -20 - 1/u = 1/ -15
-1/ u= 1/-15 + 1/20
-1/u = -4+3/60
-1/u = -1/60
-u = -60
[u =60]
The near point of a human eye is at a distance of- a)10 cm
- b)20 cm
- c)40 cm
- d)25 cm
Correct answer is option 'D'. Can you explain this answer?
The near point of a human eye is at a distance of
a)
10 cm
b)
20 cm
c)
40 cm
d)
25 cm
|
|
Abhi Prajapati answered |
The near point of the eye is the minimum distance of the object from the eye, which can be seen distinctly without strain. For a normal human eye, this distance is 25 cm. The far point of the eye is the maximum distance to which the eye can see the objects clearly. The far point of the normal human eye is infinity.
The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light- a)is scattered the most by smoke or fog
- b)is scattered the least by smoke or fog
- c)is absorbed the most by smoke or fog
- d)moves fastest in air
Correct answer is option 'B'. Can you explain this answer?
The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light
a)
is scattered the most by smoke or fog
b)
is scattered the least by smoke or fog
c)
is absorbed the most by smoke or fog
d)
moves fastest in air
|
Kiran Mehta answered |
Red colour has longer wavelength so least scattered by smoke or fog.
The lens which is used to correct myopia (shortsightedness) is- a)Both convex and concave
- b)Concave lens
- c)Converging lens
- d)Convex Lens
Correct answer is option 'B'. Can you explain this answer?
The lens which is used to correct myopia (shortsightedness) is
a)
Both convex and concave
b)
Concave lens
c)
Converging lens
d)
Convex Lens
|
Raghav Bansal answered |
Shortsightedness is corrected using a concave (curved inwards) lens which is placed in front of a myopic eye, moving the image back to the retina and making it clearer.
A student sitting on last bench in a classroom cannot see clearly words written on the blackboard. He is suffering from- a)long sightedness
- b)short sightedness
- c)astigmatism
- d)long sightedness as well as short sightedness
Correct answer is option 'B'. Can you explain this answer?
A student sitting on last bench in a classroom cannot see clearly words written on the blackboard. He is suffering from
a)
long sightedness
b)
short sightedness
c)
astigmatism
d)
long sightedness as well as short sightedness
|
|
Amit Sharma answered |
A student, who cannot read words written on blackboard from the last bench of his class room, is suffering from the myopia or short-sightedness defect of vision of eye.
Cataract can be cured by- a)Bi-focal Lens
- b)Convex Lens
- c)Surgery
- d)Concave lens
Correct answer is option 'C'. Can you explain this answer?
Cataract can be cured by
a)
Bi-focal Lens
b)
Convex Lens
c)
Surgery
d)
Concave lens
|
|
Rohan Kapoor answered |
Surgery to treat cataracts involves removing the clouded lens and replacing it with a synthetic new one. This procedure is safe and very effective.They're researching eye drops that may dissolve cataracts so patients don't have to go to surgery.
Which lens always forms diminished and erect image ?
- a)Convex lens
- b)Concave lens
- c)Converging lens
- d)Both convex and concave
Correct answer is option 'B'. Can you explain this answer?
Which lens always forms diminished and erect image ?
a)
Convex lens
b)
Concave lens
c)
Converging lens
d)
Both convex and concave
|
Kamna Science Academy answered |
A concave lens (also known as a diverging lens) is thinner in the center and thicker at the edges. When light rays pass through a concave lens, they diverge (spread out), causing the rays to appear to come from a single point on the same side of the lens as the object. This results in the formation of a virtual image.
Key characteristics of the image formed by a concave lens:
- Diminished: The image is smaller than the actual object.
- Erect: The image is upright, meaning it has the same orientation as the object.
- Virtual: The image cannot be projected on a screen because the light rays do not actually meet but only appear to do so when extended backward.
Because of these properties, a concave lens always forms a diminished, erect, and virtual image, no matter where the object is placed in front of the lens.
On the other hand, a convex lens (also known as a converging lens) can form different types of images (real and inverted or virtual and erect) depending on the position of the object relative to the lens. But it does not always form a diminished and erect image, unlike the concave lens.
In a convex lens, where is the image formed, when an object is placed at 2F ?- a)Between F and 2F
- b)At focus (F)
- c)At 2F on the other side
- d)At 2F on the same side
Correct answer is option 'C'. Can you explain this answer?
In a convex lens, where is the image formed, when an object is placed at 2F ?
a)
Between F and 2F
b)
At focus (F)
c)
At 2F on the other side
d)
At 2F on the same side
|
Gaurav Kumar answered |
At the 2F point, the object distance equals the image distance and the object height equals the image height. As the object distance approaches one focal length, the image distance and image height approaches infinity.
On a clear day, the sky appears to be more blue towards the zenith (overhead) than it does toward the horizon. This occurs because:- a)the atmosphere is denser higher up than it is at the earth’s surface.
- b)the temperature of the upper atmosphere is higher than it is at the earth’s surface.
- c)the sunlight travels over a longer path at the horizon, resulting in more absorption.
- d)none of the above is true.
Correct answer is option 'C'. Can you explain this answer?
On a clear day, the sky appears to be more blue towards the zenith (overhead) than it does toward the horizon. This occurs because:
a)
the atmosphere is denser higher up than it is at the earth’s surface.
b)
the temperature of the upper atmosphere is higher than it is at the earth’s surface.
c)
the sunlight travels over a longer path at the horizon, resulting in more absorption.
d)
none of the above is true.
|
|
Aditya Shah answered |
Because when the light of sun travel a long distance it meets with large amount of particles present in atmosphere. When they crush with small particles they got scattered due to which the blue color which have shorter wavelength, scatters most by which the sky seems blue.
A boy is wearing glasses and says that he cannot see the object kept at a distance without glasses. He is suffering from- a)Hypermetropia
- b)Cataract
- c)Presbyopia
- d)Myopia
Correct answer is option 'D'. Can you explain this answer?
A boy is wearing glasses and says that he cannot see the object kept at a distance without glasses. He is suffering from
a)
Hypermetropia
b)
Cataract
c)
Presbyopia
d)
Myopia
|
|
Raghav Bansal answered |
As Myopia is a defect of vision in which a person cannot see the distant object clearly. This can be corrected by using the concave lens of appropriate focal length
The colour which deviates most in the formation of spectrum of white light by a prism is- a)Green
- b)Yellow
- c)Red
- d)Violet
Correct answer is option 'D'. Can you explain this answer?
The colour which deviates most in the formation of spectrum of white light by a prism is
a)
Green
b)
Yellow
c)
Red
d)
Violet
|
|
Rahul Kapoor answered |
When white light falls on a glass prism, each colour in it is refracted by a different angle, from which red colour is least deviated and violet most.
A convex lens of focal length 12 cm produces a magnification of -1. The object should be placed at;- a)-12 cm
- b)-24 cm
- c)-48 cm
- d)-96 cm
Correct answer is option 'B'. Can you explain this answer?
A convex lens of focal length 12 cm produces a magnification of -1. The object should be placed at;
a)
-12 cm
b)
-24 cm
c)
-48 cm
d)
-96 cm
|
|
Pooja Shah answered |
1/v - 1/u
1/f =-1/u - 1/u
1/f = - 2/u
u=-2f
u=-24 cm
1/f =-1/u - 1/u
1/f = - 2/u
u=-2f
u=-24 cm
A person with defective eyesight is unable to see objects clearly nearer than 1.5 m. He wants to read a book placed at a distance of 30 cm from his eyes. The type of a required lens and its focal length is- a)Concave lens, f = 37.5 cm
- b)Convex lens, f = 30.5 cm
- c)Convex lens, f = 37.5 cm
- d)Concave lens, f = 30.5 cm
Correct answer is option 'C'. Can you explain this answer?
A person with defective eyesight is unable to see objects clearly nearer than 1.5 m. He wants to read a book placed at a distance of 30 cm from his eyes. The type of a required lens and its focal length is
a)
Concave lens, f = 37.5 cm
b)
Convex lens, f = 30.5 cm
c)
Convex lens, f = 37.5 cm
d)
Concave lens, f = 30.5 cm
|
|
Rahul Kapoor answered |
This person suffers from the defect of hypermetropia.
For him u = -30cm, v = -1.5 m = -150cm
Therefore, focal length of corrective lens to be used by him is
1/f = 1/v- 1/u = 1/-150 - 1/-30 = 4/150 = 37.5cm
The positive sign shows that the lens needed is a convex lens of focal length 37.5 cm.
Hence, power of lens needed
P =1/f = 100/37.5 = 2.67D
The clear sky appears blue because- a)blue light gets absorbed in the atmosphere
- b)ultraviolet radiations are absorbed in the atmosphere
- c)violet and blue lights get scattered more than lights of all other colours by the atmosphere
- d)light of all other colours is scattered more than the violet and blue colour lights by the atmosphere
Correct answer is option 'C'. Can you explain this answer?
The clear sky appears blue because
a)
blue light gets absorbed in the atmosphere
b)
ultraviolet radiations are absorbed in the atmosphere
c)
violet and blue lights get scattered more than lights of all other colours by the atmosphere
d)
light of all other colours is scattered more than the violet and blue colour lights by the atmosphere
|
|
Kuldeep Kuldeep answered |
As the Sun is made up of all the colours, Sun scatters the colour having a shorter wavelength. Rather than other colours Violet and Blue having the shorter wavelength. So the Violet and Blue colour lights get scattered more than lights of all other colours by the atmosphere. So, option c is correct friend...
The minimum distance between an object and its real image in a convex lens is (f = focal length of the lens) - a)2.5 f
- b)2 f
- c)4 f
- d)f
Correct answer is option 'C'. Can you explain this answer?
The minimum distance between an object and its real image in a convex lens is (f = focal length of the lens)
a)
2.5 f
b)
2 f
c)
4 f
d)
f
|
|
Arun Sharma answered |
Let the distance between the object and its real image formed by convex lens be d1.
Let the distance of the object from lens be x,so,the image distance from the lens is (d-x)
Let the distance of the object from lens be x,so,the image distance from the lens is (d-x)
The minimum distance between an object and its real image in a convex lens is 4f.
hence,option C is correct.
.
hence,option C is correct.
.
An object 4 cm tall is placed in front of a convex lens. It produces an image 3 cm tall. What is the magnification of the lens ?
- a)1.33
- b)12
- c)0.75
- d)11
Correct answer is option 'C'. Can you explain this answer?
An object 4 cm tall is placed in front of a convex lens. It produces an image 3 cm tall. What is the magnification of the lens ?
a)
1.33
b)
12
c)
0.75
d)
11
|
|
Rohit Sharma answered |
We know, height of the object is 4 cm h1, height of the image is 3 cm, h2.
So we have, m = h2/h1
=> m = 3/4
=> m = 0.75
Therefore, magnification of the lens is 0.75
So we have, m = h2/h1
=> m = 3/4
=> m = 0.75
Therefore, magnification of the lens is 0.75
If a lens has a focal length, F = +12 cm, then it is a- a)Can be convex or concave
- b)Convex lens
- c)Diverging lens
- d)Concave lens
Correct answer is option 'B'. Can you explain this answer?
If a lens has a focal length, F = +12 cm, then it is a
a)
Can be convex or concave
b)
Convex lens
c)
Diverging lens
d)
Concave lens
|
|
Ananya Das answered |
The focal length of convex lens is always positive. Image obtained can be either real or virtual.
A prism splits a beam of white light into seven colours because different colours have different __________________ .
- a)Speed in prism
- b)phase in prism
- c)Amplitude in prism
- d)None of these
Correct answer is option 'A'. Can you explain this answer?
A prism splits a beam of white light into seven colours because different colours have different __________________ .
a)
Speed in prism
b)
phase in prism
c)
Amplitude in prism
d)
None of these
|
Vikram Kapoor answered |
The phenomena due to which white light splits Into seven colours on passing through a prism is called dispersion. Upon passing through a medium, each of the colors travels at different speeds and hence has different angles of refraction leading to the splitting of the light.
What happens when white light is passed from air to glass prism?- a)Reflects back
- b)Bends towards normal
- c)Passes undeviated
- d)Bends away from normal
Correct answer is option 'B'. Can you explain this answer?
What happens when white light is passed from air to glass prism?
a)
Reflects back
b)
Bends towards normal
c)
Passes undeviated
d)
Bends away from normal
|
Mansi Choudhary answered |
The light pass from lower density I.e. air to higher density I.e. glass prism hence the light will bends towards the normal.
One cannot see through fog because :- a)light suffers total internal reflection at the droplets of fog.
- b)light is scattered by the droplets of fog.
- c)the refractive index of fog is infinity.
- d)fog absorbs light.
Correct answer is option 'B'. Can you explain this answer?
One cannot see through fog because :
a)
light suffers total internal reflection at the droplets of fog.
b)
light is scattered by the droplets of fog.
c)
the refractive index of fog is infinity.
d)
fog absorbs light.
|
Neha Patel answered |
light is scattered by droplets.
This happens inherently because fog is composed of water or ice crystals that remain near the surface of the earth.
It can also be known as low-lying cloud which gets influenced by topography, water bodies and wind conditions of a place.
Where should an object be placed in front of a convex lens to get a real image of the size of the object ?- a)At infinity
- b)At twice the focal length
- c)Between the optical centre of the lens and its principal focus.
- d)At the principal focus of the lens
Correct answer is option 'B'. Can you explain this answer?
Where should an object be placed in front of a convex lens to get a real image of the size of the object ?
a)
At infinity
b)
At twice the focal length
c)
Between the optical centre of the lens and its principal focus.
d)
At the principal focus of the lens
|
|
Pooja Shah answered |
At twice the focal length the image formed by convex lens is real and of the same size as object.
If the image was formed in front of the retina rather than behind the retina, then the person would need to correct the vision problem by using a:- a)converging lens
- b)diverging lens
- c)polar lens
- d)achromatic lens
Correct answer is option 'B'. Can you explain this answer?
If the image was formed in front of the retina rather than behind the retina, then the person would need to correct the vision problem by using a:
a)
converging lens
b)
diverging lens
c)
polar lens
d)
achromatic lens
|
|
Raghav Bansal answered |
Nearsighted individuals have image formed in front of the retina. They must correct the problem by wearing a lens which provides for some diverging of light prior to reaching the lens of the eye. This will move the image further from the lens of the eye and back towards the retina.
What will be the colour of sky if there is no atmosphere on the earth?- a)Dark blue
- b)Black
- c)Red
- d)White
Correct answer is option 'B'. Can you explain this answer?
What will be the colour of sky if there is no atmosphere on the earth?
a)
Dark blue
b)
Black
c)
Red
d)
White
|
Malavika Basu answered |
Raleigh Scattering of light by the atmosphere is what causes "the sky" to appear blue (and sunsets to appear red), but that "sky" is a colour of the atmosphere. If there is no atmosphere, what colour is it?
Without the atmosphere there is nothing local to act as a (secondary) source of light, so there is no light and we conventionally call objects that emit (little or) no light "black". So the non-object that is "the sky" could be called "black".
If we consider all light from "the heavens" to be the colour of "the sky" then it is clearly not "black". Even with the atmosphere and nasty light pollution from cities, the Milky Way appears rather off-white. With an even grander view of the Universe, we are told it's overall shade is Cosmic Latte, but I would take that with a pinch of salt or, perhaps, a tint of grey when it comes to human perception.
My preferred word for the apparent colour of "the sky" would be transparent rather than "black", but a pedant could argue that "transparent" is not a colour...
Which light is easily scattered ?- a)Long wavelength light
- b)Short wavelength light
- c)Sunlight
- d)Coherent light
Correct answer is option 'B'. Can you explain this answer?
Which light is easily scattered ?
a)
Long wavelength light
b)
Short wavelength light
c)
Sunlight
d)
Coherent light
|
|
Rohit Sharma answered |
The light having short wavelength can be scattered easily. For example, blue light shorter wavelength so it is scattered more easily.
The distance at which an object should be placed from a thin convex lens of focal length 10 cm to obtain a virtual image of double of its size is- a)15 cm
- b)– 5 cm
- c)-10cm
- d)5.5 cm
Correct answer is option 'B'. Can you explain this answer?
The distance at which an object should be placed from a thin convex lens of focal length 10 cm to obtain a virtual image of double of its size is
a)
15 cm
b)
– 5 cm
c)
-10cm
d)
5.5 cm
|
|
Neha Patel answered |
given : f = 10 cm , m = 2
v / u = 2
v = 2u
v = 2u -------(1)
according to lens formula ,
1/v - 1/u = 1/f
1/v - 1/u = 1/10 --------(2)
substitute (1) in (2)
1/2u - 1/u = 1/10
1 - 2 / 2u = 1/10
-1 / 2u = 1/10
-10 = 2u
u = -10/2
u = -5 cm
therfore object should be placed 5 cm away from the lens
A convergent beam of light passes through a diverging lens of focal length 0.2 m and comes to focus 0.3 m behind the lens. Find the position of the point at which the beam would converge in the absence of lens.- a)0.1 m
- b)0.22 m
- c)0.2 m
- d)0.12 m
Correct answer is option 'D'. Can you explain this answer?
A convergent beam of light passes through a diverging lens of focal length 0.2 m and comes to focus 0.3 m behind the lens. Find the position of the point at which the beam would converge in the absence of lens.
a)
0.1 m
b)
0.22 m
c)
0.2 m
d)
0.12 m
|
|
Neha Patel answered |
The image is 0.3 m to the right of the lens. This is 0.5 m TO THE RIGHT OF the left hand (image) focal point.
As explained above, concave lenses have their focal points on the opposite side of the lens to a convex lens.
So in the formula so* si = f^2 si = 0.5
f^2 = 0.2 ^2= 0.04
Therefore so = 0.04/ 0.5 = 0.08 m
This means that the object must have been 0.08 m to the left of its focal point.
which places it at 0.12m from the lens
This would be the point at which the rays of light would have converged if the lens had not been present.
It is actually a VIRTUAL OBJECT because the light never actually reaches this point.
The final point the light reaches is a REAL IMAGE because the light actually does focus at this point as can be seen by putting a paper screen there.
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?- a)diverging lens of power +1.25 D
- b)converging lens of power +1.25 D
- c)diverging lens of power -1.25 D
- d)converging lens of power -1.25 D
Correct answer is option 'C'. Can you explain this answer?
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?
a)
diverging lens of power +1.25 D
b)
converging lens of power +1.25 D
c)
diverging lens of power -1.25 D
d)
converging lens of power -1.25 D
|
|
Anjana Khatri answered |
Far point of the defective eye, v = -80 cm
Object distance, u = -∞ (-infinity)
To find :
Nature and power of the corrective lens.
Solution :
1/v - 1/u = 1/f
1/f = 1/(-80) - 1/(-∞)
1/f = - 1/80 + 0 [Since, 1/-∞ = 0]
1/f = - 1/80
f = -80 cm
Therefore, the corrective lens should be of the focal length 80 cm.
Power, P = 1 / focal length
As focal length is in centimetres, 1 m = 100 cm.
P = 100 / -80
P = -1.25 D
Therefore, the corrective lens is diverging or concave lens of power -1.5 D.
Image is formed for the shortsighted person:- a)Eye lens
- b)Before retina
- c)At retina
- d)Behind retina
Correct answer is option 'B'. Can you explain this answer?
Image is formed for the shortsighted person:
a)
Eye lens
b)
Before retina
c)
At retina
d)
Behind retina
|
Naina Kaur answered |
Short-sightedness (myopia) usually occurs when the eyes grow slightly too long, which means they're unable to produce a clear image of objects in the distance.
Drop of water behaves likes a- a)Diverging lens
- b)Concave lens
- c)Convex lens
- d)Both convex and concave
Correct answer is option 'C'. Can you explain this answer?
Drop of water behaves likes a
a)
Diverging lens
b)
Concave lens
c)
Convex lens
d)
Both convex and concave
|
|
Krishna Iyer answered |
The surface of a water drop curves outward to make a dome. This outward, or convex, curvature bends light rays inward. will act as a concave lens that bends the light rays outward. As a result, letters seen through the layer of water in a cup appear smaller than they are.
A magnifying glass is a- a)Both convex and concave
- b)Concave lens
- c)Diverging lens
- d)Convex Lens
Correct answer is option 'D'. Can you explain this answer?
A magnifying glass is a
a)
Both convex and concave
b)
Concave lens
c)
Diverging lens
d)
Convex Lens
|
|
Ꭰꮰ Ꮥꮑꭿꮶꭼ answered |
A magnifying glass is a convex lens used to make an object appear much larger than it actually is. This works when the object is placed at a distance less than the focal length from the lens.
Which lens always forms a virtual image ?- a)Concave lens
- b)Convex lens
- c)Converging lens
- d)Both convex and concave
Correct answer is option 'A'. Can you explain this answer?
Which lens always forms a virtual image ?
a)
Concave lens
b)
Convex lens
c)
Converging lens
d)
Both convex and concave
|
|
Vikram Kapoor answered |
Convex (converging) lenses can form either real or virtual images (cases 1 and 2, respectively), whereas concave (diverging) lenses can form only virtual images (always case 3). Real images are always inverted, but they can be either larger or smaller than the object.
A ray of light incident on the optical centre of a spherical lens, after refraction passes through:- a)Radius of curvature
- b)Optical centre
- c)Twice the focal length
- d)Principal focus
Correct answer is option 'B'. Can you explain this answer?
A ray of light incident on the optical centre of a spherical lens, after refraction passes through:
a)
Radius of curvature
b)
Optical centre
c)
Twice the focal length
d)
Principal focus
|
|
Ananya Das answered |
A ray of light passes through optical centre of a lens is refracted back along the same path ie. through optical centre itself.
When the light is very bright- a)the iris makes the pupil expand
- b)the iris makes the pupil contract
- c)ciliary muscles contract to make the eyelens thicker
- d)ciliary muscles expand to make the eyelens thinner
Correct answer is option 'B'. Can you explain this answer?
When the light is very bright
a)
the iris makes the pupil expand
b)
the iris makes the pupil contract
c)
ciliary muscles contract to make the eyelens thicker
d)
ciliary muscles expand to make the eyelens thinner
|
|
Ananya Das answered |
When the light is very bright the iris makes the pupil contract so as to control the quantity of light entering the eye.
Where should an object be placed in front of convex lens so as to obtain the image formed on slide projector?- a)At 2 F1
- b)At F1
- c)Between F1 and 2 F1
- d)Beyond F1
Correct answer is option 'C'. Can you explain this answer?
Where should an object be placed in front of convex lens so as to obtain the image formed on slide projector?
a)
At 2 F1
b)
At F1
c)
Between F1 and 2 F1
d)
Beyond F1
|
|
Nisha Choudhury answered |
An object should be placed between F1 and 2 F1 so as to obtain the image formation used in slide projector. This is because, the image has to be enlarged and has to form at a little larger distance from the projector.
A person has near point of his vision shifted to 50 cm. What lens must be used to see an object placed at 25 cm from the eye? What is the power of the lens?- a)A diverging lens of focal length 50 cm and power – 2 D
- b)A converging lens of focal length 50 cm and power + 2 D
- c)A converging lens of focal lens 50 cm and power – 2 D
- d)A diverging lens of focal length 50 cm and power + 2 D
Correct answer is option 'B'. Can you explain this answer?
A person has near point of his vision shifted to 50 cm. What lens must be used to see an object placed at 25 cm from the eye? What is the power of the lens?
a)
A diverging lens of focal length 50 cm and power – 2 D
b)
A converging lens of focal length 50 cm and power + 2 D
c)
A converging lens of focal lens 50 cm and power – 2 D
d)
A diverging lens of focal length 50 cm and power + 2 D
|
Coachify answered |
When object is placed at 25 cm, then a virtual image should form at 50 cm.
So, u = -25 cm, v= -50 cm.
So, 1/f = 1/-50 - 1/-25
f = 50 cm = 0.5 m
Power, P = 1/f = 1/0.5 = +2D
Therefore , a convex lens is needed.
So, u = -25 cm, v= -50 cm.
So, 1/f = 1/-50 - 1/-25
f = 50 cm = 0.5 m
Power, P = 1/f = 1/0.5 = +2D
Therefore , a convex lens is needed.
A normal eye is not able to see objects closer than 25 cm because:- a)the focal length of the eye is 25 cm.
- b)the distance of the retina from the eye-lens is 25 cm.
- c)the eye is not able to decrease the distance between the eye-lens and the retina beyond limit.
- d)the eye is not able to decrease the focal length beyond a limit.
Correct answer is option 'D'. Can you explain this answer?
A normal eye is not able to see objects closer than 25 cm because:
a)
the focal length of the eye is 25 cm.
b)
the distance of the retina from the eye-lens is 25 cm.
c)
the eye is not able to decrease the distance between the eye-lens and the retina beyond limit.
d)
the eye is not able to decrease the focal length beyond a limit.
|
Sumit Singh answered |
The eye is not able to decrease the focal length beyond a limit
The focal length of the eye lens increases when eye muscles- a)are relaxed and lens becomes thinner
- b)contract and lens becomes thicker
- c)are relaxed and lens becomes thicker
- d)contract and lens becomes thinner
Correct answer is option 'A'. Can you explain this answer?
The focal length of the eye lens increases when eye muscles
a)
are relaxed and lens becomes thinner
b)
contract and lens becomes thicker
c)
are relaxed and lens becomes thicker
d)
contract and lens becomes thinner
|
|
Krishna Iyer answered |
Cilliary muscles modify the curvature of eye lens. When eye muscles are relaxed, eye lens becomes thinner thereby are relaxed, eye lens becomes thinner thereby increase in the focal length of eye lens.
When light rays enter the eye, most of the refraction occurs at the- a)crystalline lens
- b)outer surface of the cornea
- c)iris
- d)pupil
Correct answer is option 'B'. Can you explain this answer?
When light rays enter the eye, most of the refraction occurs at the
a)
crystalline lens
b)
outer surface of the cornea
c)
iris
d)
pupil
|
Harshad Majumdar answered |
When the light rays enters the eye through a thin membrane, forms the transparent bulge on the front surface of the eyeball, called the cornea. Most of the refraction for the light rays entering the eye occurs at this outer surface of the cornea.
The phenomenon of scattering of light by the colloidal particles is called- a)Dispersion of light
- b)Tyndall effect
- c)Atmospheric scattering
- d)Atmospheric refraction
Correct answer is option 'B'. Can you explain this answer?
The phenomenon of scattering of light by the colloidal particles is called
a)
Dispersion of light
b)
Tyndall effect
c)
Atmospheric scattering
d)
Atmospheric refraction
|
|
Rahul Kapoor answered |
The phenomenon of scattering of light by the colloidal particles is called Tyndall effect. Due to this phenomenon the light rays are visible when light passes through a hole in a room or in a dense forest through the trees.
If a person with hypermetropia struggles to see objects placed closer than 50 cm, what is the power of the lens needed to correct this vision?- a)+2 D
- b)-2 D
- c)+1 D
- d)-1 D
Correct answer is option 'A'. Can you explain this answer?
a)
+2 D
b)
-2 D
c)
+1 D
d)
-1 D
|
Upsc Toppers answered |
For hypermetropia where the near point is significantly further than normal, a convex lens with a positive power, such as +2 D, is required to converge light rays correctly on the retina.
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power- a)+ 0.5 D
- b)- 0.5 D
- c)+ 0.2 D
- d)- 0.2 D
Correct answer is option 'B'. Can you explain this answer?
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power
a)
+ 0.5 D
b)
- 0.5 D
c)
+ 0.2 D
d)
- 0.2 D
|
|
Supriya dubey answered |
Person cannot see distant objects clearly. So he is suffering from myopia. The defect is corrected by using concave lens of power
The danger signals are red in colour because it is- a)strongly scattered by fog or smoke
- b)least scattered by fog or smoke
- c)least absorbed by fog or smoke.
- d)strongly absorbed by fog or smoke
Correct answer is option 'B'. Can you explain this answer?
The danger signals are red in colour because it is
a)
strongly scattered by fog or smoke
b)
least scattered by fog or smoke
c)
least absorbed by fog or smoke.
d)
strongly absorbed by fog or smoke
|
|
Amit Kumar answered |
The danger signals are red because among all other colours, red colour is scattered the least by smoke or fog. This is primarily because wavelength of red colour is the largest.
A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct ?- 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 come closer to him
- d)The far point of his eyes has receded away
Correct answer is option 'A'. Can you explain this answer?
A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct ?
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 come closer to him
d)
The far point of his eyes has receded away
|
|
Ananya Das answered |
A student sitting on the last bench of class can read the letters written on the blackboard. It means his farsight is normal. However, he cannot read the letters written in his textbook distinctly. It means he is suffering from long-sightedness (hypermetropia) and the near point of his eye has receded away
The range of vision of a normal human eye is from
- a)100 m to 25 cm
- b)infinity to 25 m
- c)1 km to 25 cm
- d)25 cm to infinity
Correct answer is option 'D'. Can you explain this answer?
The range of vision of a normal human eye is from
a)
100 m to 25 cm
b)
infinity to 25 m
c)
1 km to 25 cm
d)
25 cm to infinity
|
|
Priyanshi Sharma answered |
Because the far point of the eye is infinity one explation can be that we can see sun and moon standing on earth .this distance is much much more than focal length of our eye therefore it is considered to be infinity. we know that crystalline lens in our eyes have a power to accommodate focal length but it can't reduce focal length below 25 cm therefore the near point of our eye is 25 cm
Chapter doubts & questions for Lenses - Science and Technology Class 10 (Maharashtra SSC Board) 2025 is part of Class 10 exam preparation. The chapters have been prepared according to the Class 10 exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Class 10 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
Chapter doubts & questions of Lenses - Science and Technology Class 10 (Maharashtra SSC Board) in English & Hindi are available as part of Class 10 exam.
Download more important topics, notes, lectures and mock test series for Class 10 Exam by signing up for free.
Science and Technology Class 10 (Maharashtra SSC Board)
26 videos|131 docs|27 tests
|
|
© EduRev
|
Education Revolution
|
|
Signup to see your scores
go up within 7 days!
Access 1000+ FREE Docs, Videos and Tests
Takes less than 10 seconds to signup