Question

A dentist mirror has a radius of carvature of 3cm. how far must it be placed to give a virtual image that is magnified three time.​

Answer 1

Explanation:

R= 3cm,

f =- 3/2 = -1.5cm ( Negative sign for cancave mirror)

m = 5

We know that m= - v/u

Therefore (-5u) =( v)

Using (1/v) + (1/u) = (1/f )

(1/-5u) + ( 1/u) = (1/-1.5)

Therefore, (5u /4) = -1.5

Thus, u = -1.2 cm

The object should be placed at a distance of 1.2cm from the mirror to get 5 times magnified image.

Answer 2

Explanation:

the mirror should be placed 1.25 cm away from the dental cavity.