Define focal length.

Define focal length.
by

1 Answer

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.
by

Related questions

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.

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 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 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.

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

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

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

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

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.

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.

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 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 to turn dioptres into focal length?

Description : How to turn dioptres into focal length?

Last Answer : You’ve got it right. The dioptres = 1/focal length, so focal length = 1/dioptres. e.g. 3.3 dioptres = 1/(3.3) = 0.30303m focal length -2 dioptres = 1/(-2) = -0.5m focal length http://medical-dictionary.thefreedictionary.com/Dioptres for more info.

Can you explain the difference between a prime/fixed focal length lens and one where the focal length can be varied?

Description : Can you explain the difference between a prime/fixed focal length lens and one where the focal length can be varied?

Last Answer : With a zoom lens, you can change the focal length to zoom in or out (there's a proper name for it but it escapes me). With a prime lens, it's fixed - no zoom. Because prime lenses are ... a zoom.. You'd just use them differently and get slightly different results. I think Pros only use prime lenses.

15. An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex lens at a distance of 32 cm from the object it is found that a distinct image of the object is formed on the screen. What is the focal length of the conve -Chemistry-10

Description : 15. An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex lens at a distance of 32 cm from the object it is found that a distinct image of the object is formed on the screen. What is the focal length of the conve -Chemistry-10

Last Answer : Since, object-screen distance is double of object-lens separation, the object is at a distance of 2f from the lens and the image should be of the same size of the object.

14. An object 2 cm in size is placed 30 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the -Chemistry-10

Description : 14. An object 2 cm in size is placed 30 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the -Chemistry-10

Last Answer : Answer. hope this helps you

2. An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. [All India] -Chemistry-10

Description : 2. An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. [All India] -Chemistry-10

Last Answer : this is the answer for the respected question

1. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. [Delhi] -Chemistry-10

Description : 1. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. [Delhi] -Chemistry-10

Last Answer : Answer. hope this helps youu

17. A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging? -Physics-10

Description : 17. A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging? -Physics-10

Last Answer : Power of lens (P) = 1/f P = 1.5D f = 1/1.5 = 10/15 = 0.66 m A convex lens has a positive focal length. Therefore, it is a convex lens or a converging lens.

16. Find the focal length of a lens of power -2.0 D. What type of lens is this? -Physics-10

Description : 16. Find the focal length of a lens of power -2.0 D. What type of lens is this? -Physics-10

Last Answer : Power of lens (P) = 1/f P = -2D f = -1/2 = -0.5 m A concave lens has a negative focal length. Therefore, it is a concave lens.

15. An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed so that a sharply focused image can be obtained? Find the size and nature of the image. -Physics-10

Description : 15. An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed so that a sharply focused image can be obtained? Find the size and nature of the image. -Physics-10

Last Answer : Object distance (u) = – 27 cm Object height (h) = 7 cm Focal length (f) = – 18 cm According to the mirror formula, The negative value of image height indicates that the image formed is inverted.

12. An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image. -Physics-10

Description : 12. An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image. -Physics-10

Last Answer : Focal length of convex mirror (f) = +15 cm Object distance (u) = - 10 cm According to the mirror formula, The image is located at a distance of 6 cm from the mirror on the other ... and a value of less than 1 of magnification indicates that the image formed is virtual and erect and diminished.

11. A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram. -Physics-10

Description : 11. A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram. -Physics-10

Last Answer : Focal length of concave lens (OF1), f = – 15 cm Image distance, v= – 10 cm According to the lens formula, The negative value of u indicates that the object is placed 30 cm in front of the lens. This is shown in the following ray diagram.

10. An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed. -Physics-10

Description : 10. An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed. -Physics-10

Last Answer : Height of the Object, h0 = 5 cm Distance of the object from converging lens, u = -25 cm Focal length of a converging lens, f = 10 cm Using lens formula, Thus, the image is inverted and formed at a distance of 16.7 cm behind the lens and measures 3.3 cm. The ray diagram is shown below.

We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? -Physics-10

Description : We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? -Physics-10

Last Answer : Range of the distance of the object = 0 to 15 cm from the pole of the mirror. Nature of the image = virtual, erect, and larger than the object.

4. A spherical mirror and a thin spherical lens have a focal length of -15 cm. The mirror and the lens are likely to be -Physics-10

Description : 4. A spherical mirror and a thin spherical lens have a focal length of -15 cm. The mirror and the lens are likely to be -Physics-10

Last Answer : (a) Both are likely to be concave.

3. Find the power of a concave lens of focal length 2 m. -Physics-10

Description : 3. Find the power of a concave lens of focal length 2 m. -Physics-10

Last Answer : Focal length of concave lens (f) = 2 m Power of lens (P) = 1/f = 1/ (-2) = -0.5D

1. Find the focal length of a convex mirror whose radius of curvature is 32 cm. -Physics-10

Description : 1. Find the focal length of a convex mirror whose radius of curvature is 32 cm. -Physics-10

Last Answer : Radius of curvature (R) = 32 cm Radius of curvature = 2 × Focal length (f) R= 2f f = R/2 = 32/2 = 16 Therefore, the focal length of the given convex mirror is 16 cm.

2. The radius of curvature of a spherical mirror is 20 cm. What is its focal length? -Physics-10

Description : 2. The radius of curvature of a spherical mirror is 20 cm. What is its focal length? -Physics-10

Last Answer : Radius of curvature (R) = 20 cm Radius of curvature of the spherical mirror = 2 × Focal length (f) R = 2f f= R/2 = 20 / 2 = 10 Therefore, the focal length of the spherical mirror is 10 cm.

A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens? What would be the size of the image formed if the object is 2 cm high? With the help of a ray diagram show the formation of the image by the lens in this case. -Physics

Description : A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens? What would be the size of ... ? With the help of a ray diagram show the formation of the image by the lens in this case. -Physics

Last Answer : This is the Answe:

An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex lens at a distance of 32 cm from the object it is found that a distinct image of the object is formed on the screen. What is the focal length of the convex lens and size of the image formed on the screen? Draw a ray diagram to show the formation of the image in this position of the object with respect to the lens. -Physics

Description : An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex lens at a distance of 32 cm from the object it is found that a distinct image of the object ... diagram to show the formation of the image in this position of the object with respect to the lens. -Physics

Last Answer : Since, object-screen distance is double of object-lens separation, the object is at a distance of 2f from the lens and the image should be of the same size of the object.

An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. -Physics

Description : An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. -Physics

Last Answer : The focal length' of convex length is 7.14 cm. Solution: The given quantities are Height of the object h = 50 cm Height of the image formed h' = -20 cm Image distance v = 10 cm The image ... object distance will be So the focal length will be Thus the focal length of the convex lens is 7.14 cm

A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. -Physics

Description : A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. -Physics

Last Answer : Answer. I hope it helped you.

A concave mirror of focal length 15 cm can form a magnified, erect as well as inverted image of an object placed in front of it." Justify this statement stating the position of the object with respect to the pole of the mirror in both the cases for obtaining the images. -Science

Description : A concave mirror of focal length 15 cm can form a magnified, erect as well as inverted image of an object placed in front of it." Justify this statement stating the position of the object with respect to the pole of the mirror in both the cases for obtaining the images. -Science

Last Answer : For magnified and erect image the object is placed between pole P and focus F. For magnified and inverted image the object is placed either at focus or anywhere between F and C.

Which is a part of the eye that helps in changing the focal length of crystalline lensis? -Do You Know?

Description : Which is a part of the eye that helps in changing the focal length of crystalline lensis? -Do You Know?

Last Answer : answer:

The focal length of the lens in a photographic camera is 5 cm. What is the power of the lens? -Do You Know?

Description : The focal length of the lens in a photographic camera is 5 cm. What is the power of the lens? -Do You Know?

Last Answer : P=100/f (in cms) =100/5 1m= 100cm 0.2m= 20cm Hence,the power is 0.2 D The lens is convex as it is positive

The focal length of a convex lens is 50 cm. what is its power? -Do You Know?

Description : The focal length of a convex lens is 50 cm. what is its power? -Do You Know?

Last Answer : convex ( so focal length is positive ) given : f = 50cm or +50×10^-2m so find p =? formula p =1/f p = 1/50×10^-2 p= 100/50 P = 2

The focal length of a concave mirror is 10 cm and the distance from the mirror to the object is 5 cm . If so, what will be the reflection ?

Description : The focal length of a concave mirror is 10 cm and the distance from the mirror to the object is 5 cm . If so, what will be the reflection ?

Last Answer : The reflection will be unreal and straightforward.

+ What is the focal length of a lens of ID capacity ?

Description : + What is the focal length of a lens of ID capacity ?

Last Answer : + 1D is the focal length of a lens of power f = 1 / p = 1/1 = 1 [ Here f is the focal length , p is the power of the lens]

What is the power of a lens if the focal length of a lens is + 0.1 m ?

Description : What is the power of a lens if the focal length of a lens is + 0.1 m ?

Last Answer : If the focal length of a lens is + 0.1 m then the power of that lens will be p = 1 / f = 1 / 0.1 = 10 D [ here p power , f focus distance]

What is the focal length of a +5d capable lens ?

Description : What is the focal length of a +5d capable lens ?

Last Answer : We know that power is P = 1 / f hence the distance distance f = 1 / p = 1/5 = 0.2 m

What is the power of a convex lens with a focal length of 20 cm ?

Description : What is the power of a convex lens with a focal length of 20 cm ?

Last Answer : 20cm = 0.2 m We know , power p = 1 / f = 1 / 0.2 = + 5 D

What is the focal length of the lens ?

Last Answer : : The distance between the center of a lens and the main focus is called the focal length of that lens.

A needle 10 cm long is placed along the axis of a convex lens of focal length 10 cm such that the middle point of the neddle is at a distance of 10 cm

Description : A needle 10 cm long is placed along the axis of a convex lens of focal length 10 cm such that the middle point of the neddle is at a distance of 10 cm

Last Answer : A needle 10 cm long is placed along the axis of a convex lens of focal length 10 cm such that ... lens. Find the length of the image of the neddle.

A concave lens focal length 10 cm is placed on the axis of concave mirror of 10 cm radius at a distance of 5 cm from the mirror. An object is placed s

Description : A concave lens focal length 10 cm is placed on the axis of concave mirror of 10 cm radius at a distance of 5 cm from the mirror. An object is placed s

Last Answer : A concave lens focal length 10 cm is placed on the axis of concave mirror of 10 cm radius ... the object itself. Determine the position of the object.

A source of light and a screen are placed 90 cm apart. Where should a convex lens of 20 cm focal length be placed in order to form a real image of the

Description : A source of light and a screen are placed 90 cm apart. Where should a convex lens of 20 cm focal length be placed in order to form a real image of the

Last Answer : A source of light and a screen are placed 90 cm apart. Where should a convex lens of 20 cm focal ... form a real image of the source on the screen ?