Question

at what distance from a concave mirror of focal length 10 cm should an object 2 cm long be placed in order to get erect image 6 cm tall​

Answer 1

Answer:

magnification = hi/ ho , m=+6/+2 ,m= +3 and m=-v/u and we mirror formula get new formula for this , m=f/f-u ,+3= -10/-10-u , -30-3u=-10 ,,-40=3u means u= -40/3 cm

Answer 2

Given

Focal length of concave mirror f = -10 cm

Height of the object ho = 2 cm

Height of the image hi = 6 cm

We need to find the object distance

So we know that

Magnification m = hi/ho = 6/2 = 3 (erect image)

m = -v/u

3 = -v/u

⇒ v = -3u

Let us now consider

Mirror formula: 1/v + 1/u = 1/f

1/(-3u) + 1/u = 1/(-10)

⇒ u = -20/3 = -6.7 cm

So At -6.7cm distance from a concave mirror of focal length 10cm should an object 2cm long be placed in order to get an erect image 6cm tall.