What is lens? Explain the difference between convex and concave lenses.

What is lens? Explain the difference between convex and concave lenses.
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1 Answer

Answer :

Lens: A lens is a piece of glass or other transparent
material like plastic whose one or both side is spherical.
Types
There are two types of lenses.
1. Convex lens
2. Concave lens
Convex lens
Convex lens is thicker in the middle
and thinner at the edges.

Concave lens
Concave lens is thinner in the middle and thicker at the
edges.
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Related questions

Can an image be obtained on the screen by a concave lens? Explain your answer briefly.

Description : Can an image be obtained on the screen by a concave lens? Explain your answer briefly.

Last Answer : The ray diagram of concave lens for different positions of the object show that rays diverge out and do not meet on the other side of the lens after refraction. Therefore real image is not formed, but virtual image is formed on extending the rays backward.

Write the name of instrument in which convex lens is used

Description : Write the name of instrument in which convex lens is used

Last Answer : II. Camera III. Binoculars IV. Magnifying glass V. Contact Lens

How to know if contact lenses are expired?

Description : How to know if contact lenses are expired?

Last Answer : answer:I'm tempted to say when you can't read the old prescription, but in all seriousness I think that's a question for your doctor. Different brands and types of lens, not to mention the ... of your eyesight as opposed to the last time you had it examined, would be the determining factors.

What is the process of getting prescription lenses?

Description : What is the process of getting prescription lenses?

Last Answer : You need to get an appointment with an eye doctor and he or she will examine your eyes and write out a prescription for you. You can then take that prescription to a place that makes lenses and ask ... the lenses made at the doctor's office, but it seems to me that lenses are more expensive there.

How to Put in Contact Lenses

Description : How to Put in Contact Lenses

Last Answer : How to Put in Contact Lenses Glasses give you clear vision, but if you don't like the weight they put on your face or how you look while wearing them, one great alternative is to use contact ... on contact lenses correctly. Just follow these tips carefully and you'll have the 20/20 vision you need.

How not to be mistaken when choosing contact lenses?

Description : How not to be mistaken when choosing contact lenses?

Last Answer : How not to be mistaken when choosing contact lenses? Contact lenses are currently the most common means of correcting vision. Now on the market there are a huge number of models of contact ... is better to choose products for sensitive eyes, which will avoid the occurrence of allergic reactions.

How focal length is affected when the lens of eye becomes thicker?

Description : How focal length is affected when the lens of eye becomes thicker?

Last Answer : In order to look something near to eye, ciliary muscles make the lens thicker and its focal length becomes shorter. So the image is formed on retina instead of point beyond it.

What is a compound microscope? (1) A microscope that has one lens. (2) A microscope that has two sets of lenses : an occular lens and an eyepiece. (3) A microscope whose lenses are concave. (4) A microscope whose lenses are convex.

Description : What is a compound microscope? (1) A microscope that has one lens. (2) A microscope that has two sets of lenses : an occular lens and an eyepiece. (3) A microscope whose lenses are concave. (4) A microscope whose lenses are convex.

Last Answer : (2) A microscope that has two sets of lenses : an occular lens and an eyepiece. Explanation: A compound microscope is a microscope which uses multiple lenses to collect light from the ... lens provides the primary magnification which is compounded (multiplied) by the ocular lens (eyepiece).

Which one of the following lenses should be used to correct the defect of astigmatism? (1) Cylindrical lens (2) Concave lens (3) Convex lens (4) Bifocal lens

Description : Which one of the following lenses should be used to correct the defect of astigmatism? (1) Cylindrical lens (2) Concave lens (3) Convex lens (4) Bifocal lens

Last Answer : (1) Cylindrical lens Explanation: Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image ... lens, and cannot be corrected by standard spectacle lenses, but can be corrected by contact lenses.

Based on the diagram shown, what kind of lens is used to make the overhead projector? (a) concave lenses (b) convex lenses (c) bifocal lenses (d) flat lenses

Description : Based on the diagram shown, what kind of lens is used to make the overhead projector? (a) concave lenses (b) convex lenses (c) bifocal lenses (d) flat lenses

Last Answer : (b) convex lenses

Two concave lenses of 60 cm focal length are cemented on either side of a convex lens of 15 cm focal length. The focal length of the combination is (A) 10 cm (B) 20 cm (C) 30 cm (D) 40 cm

Description : Two concave lenses of 60 cm focal length are cemented on either side of a convex lens of 15 cm  focal length. The focal length of the combination is  (A) 10 cm  (B) 20 cm  (C) 30 cm  (D) 40 cm 

Last Answer : (C) 30 cm 

Pick up the correct statement from the following: (A) Spherical aberration may be reduced by diminishing the aperture (B) Spherical aberration may be minimised by replacing the single lens by a combination of the lenses (C) In telescope objectives, a combination of convex lens and concave lens is used (D) All the above

Description : Pick up the correct statement from the following: (A) Spherical aberration may be reduced by diminishing the aperture (B) Spherical aberration may be minimised by replacing the single lens by a ... telescope objectives, a combination of convex lens and concave lens is used (D) All the above

Last Answer : (D) All the above

Ramsden eye-piece consists of (A) Two convex lenses short distance apart (B) Two concave lenses short distance apart (C) One convex lens and one concave lens short distance apart (D) Two Plano-convex lenses short distance apart, with the convex surfaces facing each other

Description : Ramsden eye-piece consists of (A) Two convex lenses short distance apart (B) Two concave lenses short distance apart (C) One convex lens and one concave lens short distance apart (D) Two Plano-convex lenses short distance apart, with the convex surfaces facing each other

Last Answer : (D) Two Plano-convex lenses short distance apart, with the convex surfaces facing each other

What is a compound microscope? (1) A microscope that has one lens. (2) A microscope that has two sets of lenses : an occular lens and an eyepiece. (3) A microscope whose lenses are concave. (4) A microscope whose lenses are convex.

Description : What is a compound microscope? (1) A microscope that has one lens. (2) A microscope that has two sets of lenses : an occular lens and an eyepiece. (3) A microscope whose lenses are concave. (4) A microscope whose lenses are convex.

Last Answer : A microscope that has two sets of lenses : an occular lens and an eyepiece.

Which one of the following lenses should be used to correct the defect of astigmatism ? (1) Cylindrical lens (2) Concave lens (3) Convex lens (4) Bifocal lens

Description : Which one of the following lenses should be used to correct the defect of astigmatism ? (1) Cylindrical lens (2) Concave lens (3) Convex lens (4) Bifocal lens

Last Answer : Cylindrical lens

How do camera and human eye resemble with each other? What is the difference in their actions?

Description : How do camera and human eye resemble with each other? What is the difference in their actions?

Last Answer : Similarities I. The retina of eye and film of camera serve the same purpose. II. Like camera, the eye lens forms a real and inverted image. III. Pupil of eye is similar to the aperture of ... In a camera lens can be moved back and forth the image on film but eye lens cannot move.

Explain the defects in human eye.

Description : Explain the defects in human eye.

Last Answer : I. Short-sightedness (Myopia) In short-sightedness a person can see near objects clearly but distant object appear blurred. Reason When the eye lens becomes much thicker or eyeball becomes too ... before they enter the eye. They are further bent by the eye lens to meet at the retina.

Explain how eyes get used to darkness after sometime

Description : Explain how eyes get used to darkness after sometime

Last Answer : When we suddenly move from bright light to dark area, the cone cells become de-activated but rod cell do not activated immediately so we can't see things clearly. But after some time rod cells becomes ... darkness I. Cone Cell: It activate in bright light II. Rod Cell: It activate in dim light

What is a real and virtual image?

Description : What is a real and virtual image?

Last Answer : Real image The image that can be obtained on the screen is called real image. Virtual image The image that cannot be obtained on the screen is called virtual image.

Define principal axis and optical axis.

Description : Define principal axis and optical axis.

Last Answer : The line passing through the optical centre and centre of curvature of the faces of the lens is called principal axis or optical axis.

Define short-sightedness and long-sightedness.

Description : Define short-sightedness and long-sightedness.

Last Answer : In short-sightedness a person can see near objects clearly but distant object appear blurred. In long-sightedness a person can see distant objects clearly but near object appear blurred.

How long our eye takes to acquire dark adoption at its maximum?

Description : How long our eye takes to acquire dark adoption at its maximum?

Last Answer : When we suddenly move from bright light to dark area, the cone cells become de-activated but rod cell do not activated immediately so we can't see things clearly. But after some time rod cells becomes ... darkness I. Cone Cell: It activate in bright light II. Rod Cell: It activate in dim light

Upon what factor does the amount of light entering in a camera depend?

Description : Upon what factor does the amount of light entering in a camera depend?

Last Answer : The size of aperture.

Define focal length.

Description : Define focal length.

Last Answer : The distance between the optical centre (O) and focus point (F) of the lens is called focal length (f). Focal length of a convex lens is taken as positive.

Hyperrnetropia or longsight can be corrected by using : (1) Bifocal lenses (2) Cylindrical lenses (3) Concave lenses (4) Convex lenses

Description : Hyperrnetropia or longsight can be corrected by using : (1) Bifocal lenses (2) Cylindrical lenses (3) Concave lenses (4) Convex lenses

Last Answer : (4) Convex lenses Explanation: It can be corrected with convex lenses in eyeglasses or contact lenses. Convex lenses have a positive dioptric value, which causes the light to focus closer than its normal range.

Which lenses are used by people having short-sightedness? A. Convex B. Concave (Answer) C. Concavo-convex D. Plain

Description : Which lenses are used by people having short-sightedness? A. Convex B. Concave (Answer) C. Concavo-convex D. Plain

Last Answer : B. Concave (Answer)

Based on the diagram shown, what kind of lenses would Sumati need to make the telescope? (a) Concave lenses (b) Convex lenses (c) Bifocal lenses

Description : Based on the diagram shown, what kind of lenses would Sumati need to make the telescope? (a) Concave lenses (b) Convex lenses (c) Bifocal lenses

Last Answer : (b) Convex lenses

Hypermetropia or longsight can be corrected by using : (1) Bifocal lenses (2) Cylindrical lenses (3) Concave lenses (4) Convex lenses

Description : Hypermetropia or longsight can be corrected by using : (1) Bifocal lenses (2) Cylindrical lenses (3) Concave lenses (4) Convex lenses

Last Answer : Convex lenses

Pick up the correct specification of Ramsden eyepiece from the following: (A) It consists of two equal piano convex lenses (B) The curved surfaces of Plano-convex lenses face each other (C) The distance between the diaphragm and the front lens of the eyepiece is kept equal to 1/4 th of the focal length of a lens so that rays from a point on the diaphragm enter the eye as a parallel beam (D) All the above

Description : Pick up the correct specification of Ramsden eyepiece from the following:  (A) It consists of two equal piano convex lenses  (B) The curved surfaces of Plano-convex lenses face each other  (C) ... from a point on the diaphragm enter the eye as a  parallel beam  (D) All the above 

Last Answer : (D) All the above 

Pick up the correct statement from the following: (A) A refracting telescope consists optically of two lenses (B) The principal axes of both the lenses coincide the optical axis of the telescope(C) The lens nearer the object to be viewed is convex and is called objective (D) All the above

Description : Pick up the correct statement from the following: (A) A refracting telescope consists optically of two lenses (B) The principal axes of both the lenses coincide the optical axis of the telescope (C) The lens nearer the object to be viewed is convex and is called objective (D) All the above

Last Answer : (D) All the above

Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed: (i) at the centre of curvature of a concave mirror (ii) between the pole P and focus F of a concave mirror (iii) in front of a convex mirror (iv) at 2F of a convex lens (v) in front of a concave lens -Physics

Description : Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed: (i) at the centre of curvature of a concave mirror (ii) between the pole P and focus F of ... front of a convex mirror (iv) at 2F of a convex lens (v) in front of a concave lens -Physics

Last Answer : Answer. Nature of image: Real, inverted and same size image is formed at the centre of curvature. Nature of image: Virtual, enlarged and erect image is formed behind the mirror. Nature of image: Virtual ... : Virtual, erect and diminished image is formed between O and F on the same side of object.

Ray coming from an object situated at infinity, fall on a convex lens and an image is formed at a distance of 16 cm from the lens. When a concave lens

Description : Ray coming from an object situated at infinity, fall on a convex lens and an image is formed at a distance of 16 cm from the lens. When a concave lens

Last Answer : Ray coming from an object situated at infinity, fall on a convex lens and an image is formed ... . Calculate the focal length of the concave lens.

A concave lens is kept in contact with a convex lens of focal length `20 cm`. The combination works as a converging lens of focal length `100 cm`. Cal

Description : A concave lens is kept in contact with a convex lens of focal length `20 cm`. The combination works as a converging lens of focal length `100 cm`. Cal

Last Answer : A concave lens is kept in contact with a convex lens of focal length `20 cm`. The combination ... length `100 cm`. Calculate power of concave lens.

Find the focal length and power of a convex lens, which when placed in contact with a concave lens of focal length `25 cm` forms a real image `5` time

Description : Find the focal length and power of a convex lens, which when placed in contact with a concave lens of focal length `25 cm` forms a real image `5` time

Last Answer : Find the focal length and power of a convex lens, which when placed in contact with a concave ... the object placed `20 cm` from the combination.

A compound lens has been formed by joinined a convex and a concave lens, each of focal length 30 cm. what is the focal length of the combination? What

Description : A compound lens has been formed by joinined a convex and a concave lens, each of focal length 30 cm. what is the focal length of the combination? What

Last Answer : A compound lens has been formed by joinined a convex and a concave lens, each of focal length 30 ... of the combination? What will be the power ?

The focal length of a concave-convex lens of radii of curvature 5 cm and 10 cm is 20 cm. what will be its focal length in water ? Given `.^(a)mu_(w) =

Description : The focal length of a concave-convex lens of radii of curvature 5 cm and 10 cm is 20 cm. what will be its focal length in water ? Given `.^(a)mu_(w) =

Last Answer : The focal length of a concave-convex lens of radii of curvature 5 cm and 10 cm is 20 cm. what will be its ... water ? Given `.^(a)mu_(w) = 4//3`.

Which one of the following can be used to focus sunlight? A. Plane mirror B. Concave lens C. Concave mirror D. Convex mirror

Description : Which one of the following can be used to focus sunlight? A. Plane mirror B. Concave lens C. Concave mirror D. Convex mirror

Last Answer : ANSWER: C

When light enters a closed room through a small hole in the door, the image of an outside building appears as inverted on the opposite wall. This is because (a) The hole acts as a convex lens (b) Light takes curvature at the edges of the hole (c) Of rectilinear propagation of light (d) The hole acts as a concave lens

Description : When light enters a closed room through a small hole in the door, the image of an outside building appears as inverted on the opposite wall. This is because (a) The hole acts as a convex lens (b) ... the edges of the hole (c) Of rectilinear propagation of light (d) The hole acts as a concave lens

Last Answer : Ans:(b)

Which of the following can be used as a burning glass? (a) Plane mirror (b) Convex mirror (c) Concave lens (d) Concave mirror

Description : Which of the following can be used as a burning glass? (a) Plane mirror (b) Convex mirror (c) Concave lens (d) Concave mirror

Last Answer : Ans:(d)

Which one of the following is used to remove Astigmatism for a human eye? (1) Concave lens (2) Convex lens (3) Cylindrical lens (4) Prismatic lens

Description : Which one of the following is used to remove Astigmatism for a human eye? (1) Concave lens (2) Convex lens (3) Cylindrical lens (4) Prismatic lens

Last Answer : (3) Cylindrical lens Explanation: In Astigmatism, eye cannot see objects in two orthogonal directions clearly simultaneously. This abnormality is removed by using cylindrical lens.

Which among the following lens is used to correct Presbyopia? (1) Concave (2) Convex (3) Cylindrical (4) Bifocal

Description : Which among the following lens is used to correct Presbyopia? (1) Concave (2) Convex (3) Cylindrical (4) Bifocal

Last Answer : (4) Bifocal Explanation: Presbyopia is a condition associated with aging of the eye those results in progressively worsening ability to focus clearly on close objects. By far the most common treatment 4 for presbyopia is bifocal or pro gressive lens eyeglasses.

What type of lens is used to correct vision of a person suffering from Myopia? (1) Convex lens (2) Concave lens (3) Crossed lens (4) Cylindrical lens

Description : What type of lens is used to correct vision of a person suffering from Myopia? (1) Convex lens (2) Concave lens (3) Crossed lens (4) Cylindrical lens

Last Answer : (2) Concave lens Explanation: Near-sightedness, also known as short-sightedness and myopia, is a condition of the eye where light focuses in front of, instead of on, the retina. This causes distant objects to be blurry while close objects appear normal.

Vehicles use ______ to see the objects coming from behind. (1) Concave lens (2) Convex lens (3) Convex mirror (4) Concave mirror

Description : Vehicles use ______ to see the objects coming from behind. (1) Concave lens (2) Convex lens (3) Convex mirror (4) Concave mirror

Last Answer : (2) Convex lens Explanation: Convex mirror is used in rear view mirror of vehicles; so that the driver can see the traffic coming from behind. The field of view is widest in case of a convex mirror, which enables it to show a wider area from behind.

Persons suffering from myopia are advised to use – (1) convex lens (2) concave lens (3) piano-convex lens (4) plano-concave lens

Description : Persons suffering from myopia are advised to use – (1) convex lens (2) concave lens (3) piano-convex lens (4) plano-concave lens

Last Answer : (2) concave lens Explanation: A concave lens is used to correct short-sightedness (myopia). In myopia, images are formed in front of the retina, resulting in a blurred image. This occurs when the ... too long or the refractive powers of the cornea and lens of the eye are relatively too strong.

Magnifying Glass is basically a – (1) Plano-concave lens (2) Concave lens (3) Convex lens (4) Cylindrical lens

Description : Magnifying Glass is basically a – (1) Plano-concave lens (2) Concave lens (3) Convex lens (4) Cylindrical lens

Last Answer : (3) Convex lens Explanation: A magnifying glass is a convex lens that is used to produce a magnified image of an object. The magnification of a magnifying glass depends upon where it is placed between the user's eye and the object being viewed, and the total distance between them.

`Short-sight' in human eye can be corrected by using proper – (1) convex lens (2) concave lens (3) cylindrical lens (4) bifocal lens

Description : `Short-sight' in human eye can be corrected by using proper – (1) convex lens (2) concave lens (3) cylindrical lens (4) bifocal lens

Last Answer : (2) concave lens Explanation: Scintillation or twinkling is generic terms for variations in apparent brightness or position of a distant luminous object viewed through a medium. If ... is termed astronomical scintillation; within the atmosphere, the phenomenon is termed terrestrial scintillation.

A camera uses a ______ to form an image on a piece of film at the back. (1) convex lens (2) concave lens (3) diverging lens (4) none of these

Description : A camera uses a ______ to form an image on a piece of film at the back. (1) convex lens (2) concave lens (3) diverging lens (4) none of these

Last Answer : (1) convex lens Explanation: A camera consists of three main parts. • The body which is light tight and contains all the mechanical parts. • The lens which is a convex lens. • The film or a charged couple device in the case of a digital camera.

Spectacles used for viewing 3D films have – (1) Bifocal lens (2) Convex lens (3) Concave lens (4) Polaroid

Description : Spectacles used for viewing 3D films have – (1) Bifocal lens (2) Convex lens (3) Concave lens (4) Polaroid

Last Answer : (4) Polaroid Explanation: A polarized 3D system uses polarization glasses to create the illusion of three-dimensional images by restricting the light that reaches each eye, an example of stereoscopy. ... and blocks the light polarized in the opposite direction, each eye sees a different image.

A simple microscope consists of : (1) a short focus convex lens (2) a long focus convex lens (3) a short focus concave lens (4) a long focus concave lens

Description : A simple microscope consists of : (1) a short focus convex lens (2) a long focus convex lens (3) a short focus concave lens (4) a long focus concave lens

Last Answer : (1) a short focus convex lens Explanation: Simple microscope - light microscope consisting of a short focus single convex lens is used to produce an enlarged image. The magnifying glass was ... object viewed and one lens, increasing the visibility of the object by some amount (magnification).

Which one of the following is used to remove Astigmatism for a human eye? (1) Concave lens (2) Convex lens (3) Cylindrical lens (4) Prismatic lens

Description : Which one of the following is used to remove Astigmatism for a human eye? (1) Concave lens (2) Convex lens (3) Cylindrical lens (4) Prismatic lens

Last Answer : (3) Cylindrical lens Explanation: A cylindrical lens is a lens which focuses light into a line instead of a point, as a spherical lens would.