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Spherical Concave Mirror?
An object whose height is 5.3 cm is at a distance of 8.5 cm from a spherical concave mirror. Its image is real and has a height of 11.1 cm. Calculate the radius of curvature of the mirror.
How far from the mirror is it necessary to place the above object in order to have a virtual image with a height of 11.1 cm?
1 Answer
- Andrew SmithLv 74 years agoFavorite Answer
The centre of curvature is twice the focal length.
As the image is real we know that the object is outside the focal point.
And that the image is on the same side of the mirror.
You could use 1/do + 1/di = 1/f
You know that hi/ho = di/do
but hi / ho = 11.1 / 5.3
And we know that do = 8.5 so therefore di = 8.5 * 11.1/ 5.3
Now substitute into f = 1 / ( 1/do + 1/di) = 1/ ( 1/8.5 + 1/ ( 8.5 * 11.1/5.3) ) = 5.763 cm
To get a virtual image of the same size as this real image the object must be the same distance FROM the focal point but on the other side of it.
As this object is 8.5 - 5.763 from the focal point then the other point must be inside the focal point by the same amount.
= 5.763-( 8.5 - 5.763) = 3.01 cm from the mirror.
To do part
