Plane Mirror - Distance to Focus for Clear Selfie

[Jess_18033152]

Homework Statement

Suppose that you want to take a mirror selfie, standing 3.05 m in front of a plane mirror.

Calculate the distance that the camera will focus to, to get a clearly focused image of your beautiful self.

Homework Equations

d0 = di

The Attempt at a Solution

Would I be correct in saying that the distance the camera needs to be to focus is the same distance as the said person is already standing from the plane mirror? So the answer would be 3.05m?

 

[ehild]

Homework Statement

Suppose that you want to take a mirror selfie, standing 3.05 m in front of a plane mirror.

Calculate the distance that the camera will focus to, to get a clearly focused image of your beautiful self.

Homework Equations

d0 = di

The Attempt at a Solution

Would I be correct in saying that the distance the camera needs to be to focus is the same distance as the said person is already standing from the plane mirror? So the answer would be 3.05m?

What is di? The distance of what from what? Where is the camera? How far from the mirror?

 

[Jess_18033152]

What is di? The distance of what from what? Where is the camera? How far from the mirror?

All I've been given for this question is what I gave you.
di is the distance the image is seen from the mirror. The camera is held by the said person taking the picture. I assume distance from the mirror to focus?

 

[ehild]

All I've been given for this question is what I gave you.
di is the distance the image is seen from the mirror. The camera is held by the said person taking the picture. I assume distance from the mirror to focus?

If it is a real object, the camera had to be focused at the distance of the object. Now, the object is your mirror image, and you hold the camera, close to your eyes. How far is the camera from the object now?

 

[Jess_18033152]

If it is a real object, the camera had to be focused at the distance of the object. Now, the object is your mirror image, and you hold the camera, close to your eyes. How far is the camera from the object now?

Would this mean that I need to use the following equation instead?

1/d0 + 1/di = 1/f ?

 

[ehild]

No, the problem does not ask where the image with the camera will be. It asks how far it "feels" the object. And the object is behind the mirror, your mirror image.
You stand in front of a plane mirror, at d distance from it, You see your image behind the mirror. How far from the mirror does your image appear?
Just try, see yourself in a mirror. Walk closer to the mirror, what happens with your image?
Do you have a camera which shows distance? Stand 1 m far from the mirror, focus the camera at your mirror image and see, at what distance your image on the camera is sharp.

 

[Jess_18033152]

No, the problem does not ask where the image with the camera will be. It asks how far it "feels" the object. And the object is behind the mirror, your mirror image.
You stand in front of a plane mirror, at d distance from it, You see your image behind the mirror. How far from the mirror does your image appear?
Just try, see yourself in a mirror. Walk closer to the mirror, what happens with your image?
Do you have a camera which shows distance? Stand 1 m far from the mirror, focus the camera at your mirror image and see, at what distance your image on the camera is sharp.

The image is 2 x the distance from the mirror so my answer would be
2 x 3.05 = 6.1 m

 

[ehild]

The image is 2 x the distance from the mirror object so my answer would be
2 x 3.05 = 6.1 m

Your image is at the same distance from the mirror as your distance is, as you wrote in the OP that di = do. But your result is correct now.