Question

A concave mirror of focal length 10 cm forms an upright and diminished image of a real object placed at a distance of 5 cm from the mirror. Is this true or false?

Answer 1

Given,

The focal length of the concave mirror, f=10 cm

The object distance, o=5 cm

From the mirror formula, we have,

`(1)/(f)=(1)/(o)+(1)/(i)`

Where i is the image distance.

On substituting the known formula,

`\begin{gathered} (1)/(10)=(1)/(5)+(1)/(i) \\ \Rightarrow(1)/(i)=(1)/(10)-(1)/(5) \\ =-(1)/(10) \\ \Rightarrow i=-10\text{ cm} \end{gathered}`

And the magnification is given by,

`m=(-i)/(o)`

On substituting the known values,

`\begin{gathered} m=(-(-10))/(5) \\ =2 \end{gathered}`

Thus the object is not diminished, it is magnified.

Thus the given statement is false.