Where Must The Film Be Placed If A Camera Lens Is To Make A Sharp Image Of An Object Far Away?

Excursions in Physics

Homework, Chapter 19:

Optical Instruments

(this is Chapter 19 of Adventures in Physics , available only online)

Ch nineteen, Optical Instruments; one through 10

| Dorsum to 3050's Home Page | Back to Agenda | ToC, Ch 19 | Ch xx, Wave Optics |

Homework for Affiliate 19, Optical Instruments

1. As the aperature in a pivot-hole camera increases, the image becomes brighter simply will no longer be in focus. A lens is now necessary. Explain what the lens does.

As the pin-pigsty becomes larger, lite that originated from a tiny indicate on the object is allowed to spread out to a big circle on the image. This makes the image fuzzy. A lens focuses the calorie-free that originated from a tiny point on the object back downward to a tiny bespeak on the image. This means the prototype is sharp or clear.

2. What is meant by "depth of field"? How or why does "depth of field" depend upon the lens opening?

"Depth of field" is the distance over which an object volition still produce a reasonable or passably abrupt image. That is "depth of field" is the range of object distances that withal produce an image distance that corresponds to the location of the film.

For a tiny pin-hole camera, with a tiny opening, the depth of field is space. As the lens opening (call the apeture) gets larger, the depth of field gets smaller and smaller.

3. If you focus first on a person near a camera and and so focus on the groundwork far away, practice you move the photographic camera'due south lens toward the film or abroad from the film?

As the object moves further from the lens or as the object distance increases, the epitome distance must subtract or we must move the film and lens closer to each other.

4. When a lens is used to assistance a nearsighted person run into a distant object, what kind of image is produced by this lens and where is it located?

The lens produces a virtual image that is closer to the eye than the actual object is. This new prototype -- this virtual paradigm -- is closer than the patient's far signal. That is, this new epitome -- this virtual paradigm -- is located in the region in which the patient can run into it clearly.

5. In terms of the virtual image produced, explain what effect a converging eyeglass lens has on light reaching the center. For what kind of vision condition -- nearsightedness or farsightedness -- is this the right corrective lens?

A converging lens can produce a virtual image that is further away than the object (this was the case for the final experiment yous did in the Image Formation lab). This virtual image, then, can be beyond a farsighted person's virtually point and, thus, be located in the region that such a person can see conspicuously.

6. When a lens is used to help a farsighted person run across a afar object, what kind of image is produced by this lens and where is it located?

The converging lens produces a virtual image that is farther from the eye than the actual object is. This new image -- this virtual epitome -- is farther than the patient'south most signal. That is, this new epitome -- this virtual paradigm -- is located in the region in which the patient can see it clearly.

vii.  Why is your vision sharper or clearer in bright sunlight than in a moderately lighted room?

In bright sunlight, the iris of the center becomes smaller and your "depth of field" increases. Your eye behaves more than like a pivot-hole photographic camera. This makes the image on your retina sharper.

8. If a person tin can conspicuously see far distant objects and even so see them clearly until they are 75 cm abroad, how would you draw that person's vision? What is their far bespeak? What is their near point? It is more than comfy to read a book when it is well-nigh 25 cm away. What sort of eyeglass lenses would let this person to read a book held about 25 cm abroad.

The person is farsighted with a near signal of 75 cm. Since they can see far afar objects conspicuously, their far bespeak is infinity. Their near point is 75 cm.

When holding a book at 25 cm, we want to form a virtual image that is 75 cm backside the eyeglass lens. This requires a

9. If a person can clearly see nearby objects and withal run across them until they are near 150 cm away, how would you describe that person's vision? What sort of eyeglass lenses volition allow this person to see a far-distant billboard?

This person is nearsighted with a far signal of 150 cm.

Such a nearsighted center can exist helped with a diverging lens.

10. Explain how a elementary magnifier works. What kind of lens tin can be used equally a simple magnifier?

A converging lens may be used as a simple magnifier by producing a virtual image at infinity -- or, at to the lowest degree, far abroad from the heart -- then it tin be conspicuously focused onto the retina.

| Back to 3050's Home Folio | Back to Calendar |

Typical multiple-gauge questions over this material:

1. Your vision is sharpest when your pupil is

a) dilated or opened wide

b) constricted or made tiny

c) blue

d) dark-brown

two. Initially, a camera is focused at some far-distant mountains. It is and then adapted to focus on a nearby person. To do this, the lens

a) is moved closer to the film.

b) is moved farther from the moving-picture show.

c) is "opened" to larger apeture or larger opening.

d) is "shut downwardly" to a smaller apeture or smaller opening.

3. A compound microscope

a) forms a virtual image with its objective lens; this is then viewed with the eyepiece.

b) forms a existent image with its objective lens; this is then viewed with the eyepiece.

c) forms a virtual image with its objective lens which can be projected onto a ground drinking glass or viewing screen.

d) forms a virtual epitome which is right-side-up and enlarged.

4. A chemical compound microscope

a) uses a diverging lens as an objective lens to form a virtual image.

b) uses a converging lens as an objective lens to form a virtual prototype.

c) uses a diverging lens as an eyepiece lens to form a virtual image.

d) uses a converging lens as an objective lens to grade a real paradigm.

5. The eyepiece in a compound microscope is used

a) to project a real prototype onto a ground glass or viewing screen.

b) as a simple magnifier to view the real prototype produced by the objective lens.

c) as a converging lens to re-capsize the image and then it is correct-side-up.

d) to invert the epitome a second time to make information technology right-side-upwardly.

6. The objective lens in an astronomical telescope forms

a) a virtual image at infinity.

b) a virtual image beyond the eyepiece.

c) a existent epitome at infinity.

d) a real epitome that is viewed by the eyepiece.

7. The eyepiece in a telescope forms

a) a virtual image that is correct-side-up.

b) a virtual image that can be comfortably viewed by the eye.

c) a real prototype that can be projected on a viewing screen.

d) a real image that is correct-side-up.

8. Vision for a nearsighted eye tin can be improved with glasses that are

a) converging

b) diverging

9. Vision for a farsighted eye tin can exist improved with glasses that are

a) converging

b) diverging

10. The "nearly point" of an eye is

a) the farthest distance that center can comfortably see.

b) ever 25 cm

c) the closest distance that heart can confortably see.

d) infinity.

11. The "far bespeak" of an eye is

a) the farthest distance that centre can comfortably see.

b) always 25 cm

c) the closest distance that eye tin can confortably see.

d) infinity.

Answers to typical multiple-gauge questions over this material:

1. Your vision is sharpest when your student is

a) dilated or opened broad

b) constricted or made tiny

Recall that the image of a pin-hole photographic camera is always in focus equally long as the pigsty actually is a pin-hole. As the size of the opening increases, the paradigm becomes fuzzy and, somewhen, a lens is required to focus the image. With a lens, the altitude from object to lens now becomes important and focusing on a nearby person means the far-afar mountains will not be entirely abrupt.

c) blueish

d) brown

2. Initially, a camera is focused at some far-distant mountains. Information technology is then adjusted to focus on a nearby person. To practice this, the lens

a) is moved closer to the pic.

b) is moved farther from the film.

c) is "opened" to larger apeture or larger opening.

d) is "shut down" to a smaller apeture or smaller opening.

Look at ii ray diagrams from the previous chapter. Here an image is formed by a lens with a 10-cm focal length. Initially, the object is 30 cm away.

This produces an image that is most fifteen cm from the lens.

In the 2nd diagram, the object is twenty cm from the lens and an prototype is produced twenty cm beyond the lens.

This means that decreasing the object distance volition increase the image distance. Therefore, irresolute from an object very far away to an object nearby ways the image distance -- the distance from the lens to the picture show -- will increase. Then the lens must exist moved away from the film.

3. A compound microscope

a) forms a virtual epitome with its objective lens; this is then viewed with the eyepiece.

b) forms a real image with its objective lens; this is so viewed with the eyepiece.

c) forms a virtual epitome with its objective lens which tin be projected onto a basis glass or viewing screen.

d) forms a virtual image which is correct-side-up and enlarged.

iv. A chemical compound microscope

a) uses a diverging lens as an objective lens to form a virtual image.

b) uses a converging lens as an objective lens to form a virtual paradigm.

c) uses a diverging lens as an eyepiece lens to form a virtual paradigm.

d) uses a converging lens as an objective lens to form a real image.

5. The eyepiece in a compound microscope is used

a) to project a existent image onto a ground glass or viewing screen.

b) as a elementary magnifier to view the real image produced by the objective lens.

c) equally a converging lens to re-invert the paradigm so information technology is right-side-up.

d) to capsize the image a 2nd time to make it right-side-upwards.

six. The objective lens in an astronomical telescope forms

a) a virtual image at infinity.

b) a virtual epitome beyond the eyepiece.

c) a real paradigm at infinity.

d) a real image that is viewed by the eyepiece.

7. The eyepiece in a telescope forms

a) a virtual prototype that is correct-side-upwards.

b) a virtual image that can exist comfortably viewed by the eye.

c) a real image that can be projected on a viewing screen.

d) a real image that is right-side-up.

eight. Vision for a nearsighted eye tin can exist improved with glasses that are

a) converging

b) diverging

ix. Vision for a farsighted eye tin can be improved with glasses that are

a) converging

b) diverging

10. The "well-nigh point" of an middle is

a) the uttermost distance that middle tin can comfortably meet.

b) ever 25 cm

c) the closest altitude that eye tin confortably see.

d) infinity.

11. The "far indicate" of an middle is

a) the farthest distance that center tin comfortably see.

b) ever 25 cm

c) the closest distance that centre tin can confortably run into.

d) infinity.

| Back to 3050's Home Page | Back to Calendar | ToC, Ch nineteen | Ch xx, Wave Optics |

(C) 2003, Doug Davis; all rights reserved

Source: https://ux1.eiu.edu/~cfadd/3050/Hmwk/Ch19.html

Posted by: nunleyalung1980.blogspot.com

Share this post