Question

A convex mirror of focal length 10cm is kept at a distance of 30cm front of a 4cm high object.Find the height of the image of the object?

Answer 1

`"the length of the image is 1 cm."`

Explanation:

`-1/f=1/u-1/(u')`

`"where f is the focal length, u is the distance between the object and the mirror, "`u'`" is the distance from the image to the mirror."`

`"Since the focus and the image are behind the mirror, their signs is negative."`

• Convex mirrors create a virtual image.
• The image is smaller than the object.

`f=10" " cm`
`u=30" "cm`
`"let us calculate the image length using formula."`

`-1/10=1/30-1/(u^')`

`1/(u^')=1/10+1/30`

`1/(u^')=(3+1)/30`

`1/(u^')=4/30`

`u^'=7.5" " cm`

`g/c=(u')/u`

`"where g is the length of the image, c is the length of the object."`

`g/4=(u^')/u`

`g/4=(7.5)/30`

`g/4=1/4`

`g=1 cm`