Calculate Image Diameter of Sun in Concave Mirror with Given θ and f

AI Thread Summary
The discussion revolves around calculating the diameter of the sun's image formed by a concave mirror, given its subtended angle θ and focal length f. Participants express confusion about whether an image can be formed, considering the sun's vast size and its distance, often treating it as if it were at infinity. Clarifications highlight that while light rays from the sun strike the mirror, they do not all reflect like a plane mirror; instead, they converge to form an image. By analyzing specific rays from the sun's top and bottom, one can determine the extent of the image. The analogy of the sun's reflection in a skyscraper is used to illustrate that an image can indeed be formed despite the sun's size.
vkash
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Homework Statement



The sun of (diameter D) subtends an angle of θ radians at the pole of the concave mirror of focal length f. The diameter of the image of the sun formed by mirror is _____

Homework Equations



1/v+1/u=1/f

The Attempt at a Solution


confused with question. Either i am getting zero or infinity(sun is too large!)..
 
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The sun can be taken to be at infinity so the image of the sun will be formed... where?
Light rays striking the centre of the mirror (from the top/bottom of the sun) will be reflected at same angle.
Can you get it from this?
 
technician said:
The sun can be taken to be at infinity so the image of the sun will be formed... where?
Light rays striking the centre of the mirror (from the top/bottom of the sun) will be reflected at same angle.
Can you get it from this?

when light strike at the pole of the concave mirror they are reflected like plane mirror. So No image should form?
Am i correct?
 
vkash said:
when light strike at the pole of the concave mirror they are reflected like plane mirror. So No image should form?
Am i correct?

No, only one ray from each point on the sun strikes the pole of the mirror. All the other rays strike somewhere else.
You do know what direction one other special ray will reflect, and every other ray from a given point on the sun will reflect through that same point - forming an image of that point.
Choosing a point on the "top" of the sun, and another on the "bottom"of the sun will enable you to locate the extent of the image of the sun.
 
vkash said:
when light strike at the pole of the concave mirror they are reflected like plane mirror. So No image should form?
Am i correct?

btw - have you ever seen an image of the sun "reflected in the side of a sky scraper"?
That should answer your question about whether an image is formed after reflection in a plane mirror.
 
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