## 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.