Respuesta :
Answer:
2.4 m
Explanation:
Plane Mirror: It is a type of mirror whose reflecting surface is plane. it produces an image of an object behind it at a distance equal to the object lying in front of the mirror.
According to the question, the person has to take the photo of himself who is looking at the mirror.
Let us assume that the person is standing in front of a plane mirror at a distance of 1.2 m.
Due to the reflection of light, the image of the person will be formed at a distance 1.2 m behind the mirror. This means the image of the person is 2.4 m apart from him.
As the person could take the picture of his own image from the classic camera in his hand. This means the image of the person will act as an object for the classic camera to which he is going to focus on which is at a distance of 2.4 m.
Hence, the person will choose a distance of 2.4 m.
Focus length is the distance of optics from the point of convergence of light rays to create a sharp image of the object.
The distance of the focus must be 2.4 meters.
How to select the distance for ideal focus length?
Focus length is the distance of optics from the point of convergence of light rays to create a sharp image of the object. Focus length represents in the millimetres.
In the given problem, the person is standing in front of the plane mirror. A plane mirror is the mirror with a flat reflective surface.
The image formed by the plane mirror is virtual, erect and the equal to the size of the person or thing.
Given information-
The distance of person from the mirror is 1.2 m.
As the image in the plane mirror appears at the equivalent distance to the object, thus the distance of the image of the person is,
[tex]d_i=1.2 \rm m[/tex]
Thus the distance of the image of the person appears is 1.2 meters behind the mirror.
To take the photo of this image, the distance of the focus should be equal to the sum of the distance of the image inside the mirror to the distance of person front of the mirror. Thus,
[tex]d_f=d_p+d_i\\d_f=1.2+1.2\\d_f=2.4 \rm m[/tex]
Hence the distance of the focus must be 2.4 meters.
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