Monday, January 11, 2010

Getting bigger or smaller ?

Khas untuk murid 5um and 5 ukm..

In any optical system where images are formed from objects, the ratio of the image height, hi, to the object height, ho is known as the magnification, m.

m = hi/ho

For a plane mirror, the height of the image is the same as the height of the object, so the magnification is simply m = hi/ho = 1.

If the magnification is greater than 1,
the image is larger than the object and is said to be magnified.

If the magnification is less than 1, the image is smaller than the object so the image is said to be diminished.

Example:
Question:
A concave mirror forms an image that is 3.6 cm high. The height of the object is 1.2 cm. Calculate the magnification of the mirror.

Suggested solution,

Step 1 : Identify what is given and what is asked.
Image height hi = 3.6 cm
Object height ho = 1.2 cm
Magnification m = ?

Step 2 : Substitute the values and calculate m.
m = hi/ho
= 4.8/1.6
= 3
The magnification is 3 times.

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