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A student has focussed the image of an object of height 3 cm on a white screen using a concave mirror of focal length 12 cm. If the distance of the object from the mirror is 18 cm, find the values of the following: Distance of the image from the mirror;  Height of the image. Please answer these questions.
Asked by jayeshsah1995 | 04 Mar, 2023, 06:33: PM

Given that:

Height of the object, h = 3 cm

The focal length of the concave mirror, f = -12 cm (negative sign indicates concave mirror)

Distance of the object from the mirror, u = 18 cm

i)

Now, according to the mirror formula, we know that:

1/f = 1/v - 1/u

Now, by substituting the given data, we get:

1/12 = 1/v - 1/18

Solving for v, we get:

v = 36 cm

ii)

In order to determine the height of an image, we need to use the magnification formula:

m = -v/u

m = -36/18 = -2

Thus, the image is twice as big as the object but inverted.

h' = -2 x 3 cm = -6 cm

Answered by Jayesh Sah | 04 Mar, 2023, 06:36: PM

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