# Why does looking through a traw improve the focus or resolution you see?

• philip041
This allows for a larger depth of field, which means more of the image is in focus and easier to read.In summary, the reason you can read the title of a book on your shelf even with poor eyesight is because of the limited rays near the axis of your eye when looking through a curled hand or a hole. This principle also applies to optics, such as cameras, and is why it's easier to read in bright light. The expanded iris in bright light also allows for a larger depth of field, making the image more in focus and easier to read.

#### philip041

When I curl my hand up and look through it, even though I have terrible eye sight I can read the title of a book on my shelf even though I can't if I'm not wearing my glasses. Why is this? I just had a lecture on SNOM, (Scanning Nearfield Optical Microscope), where the lecturer made a comparison with this.

Your imperfect eye doesn't focus all the rays of light to a single point
The rays at the edge of the field of view have to be bent most and so are affected most by any error in the bending. By putting a hole in front of your eye (it works with just your fingers making a loop) you limit the rays to only those near the axis which are ebtn least.

The same thing applies to all optics, it's why your camera takes sharper pictures with the iris stopped down.

You can also read better when in bright light, and not only for the obvious reason. When your eye is stimulated by bright light, your iris expands significantly, constricting your pupil to more of a pinhole.

## 1. Why does looking through a traw improve the focus or resolution you see?

Looking through a traw improves focus and resolution because it acts as a magnifying glass. The curved shape of the traw bends light rays, making them converge at a single point. This allows for a clearer and larger image to be seen.

## 2. How does the curvature of a traw affect the focus?

The curvature of a traw affects the focus by bending light rays and causing them to converge at a single point. This creates a sharper and more focused image compared to looking at the object with the naked eye.

## 3. Can a traw improve focus on all objects?

No, a traw can only improve focus on objects that are within its focal length. Objects that are too far away or too close will not be in focus when viewed through a traw.

## 4. Why do some traws have a larger focal length than others?

The focal length of a traw depends on its curvature. A traw with a larger curvature will have a shorter focal length, while a traw with a flatter curvature will have a longer focal length. This is why some traws are better for viewing distant objects, while others are better for close-up viewing.

## 5. Is there a limit to how much a traw can magnify an object?

Yes, there is a limit to how much a traw can magnify an object. This limit is determined by the curvature and size of the traw. If the traw is too curved or too small, it may create distortions or a blurry image instead of magnifying the object.