ICSE Class 9 Answered

Discuss the position and nature of image formed by a concave mirror when an object is moved from infinity towards the pole of mirror.

Asked by Ms123736 | 29 Jan, 2016, 07:59: PM

Expert Answer

Position of object	Position of image	Size of image	Nature of image
At infinity	At focus F	Diminished to point size	Real

Two rays AD and BE are coming from object AB which is at infinity. After reflection, these rays pass through the focus F as DF and EF.

Position of object	Position of image	Size of image	Nature of image
At infinity	At focus F	Highly diminished	Real and inverted

Consider two rays AP and BD coming from the same point of the object. These rays are parallel as the object is very far.
AP is striking at pole P and hence reflects along PA₁.
Similarly, BD is reflected along DA₁ such that ÐBDC = ÐA₁DC.
Thus, image FA₁ is real as well as inverted.

Answered by Faiza Lambe | 30 Jan, 2016, 07:19: PM

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