Question

Rajashree wants to get an inverted image of height 5 cm of an object kept at a distance of 30 cm from a concave mirror .The focal length of the mirror is 10 cm.At what distance from the mirror should she plays the screen ?What will be the type of the image, and what is the height of the object ?
plzzz explain all the steps because it's too confusing in the book

Answer 1

Height of the object =2 cm

U(object distance) = -15 as u is always negative

F = -10 (as it is always negative for concave miror and lens )

1/F =1/v + 1/u

-1/10 = 1/v + (-1/15)

-1/10 +1/15 =v

-3+2/30 =v

V=-30cm

Hi/Ho = - V/U

Hi /2 = -(-30/15)

Hi =-30×2÷15

Hi =-4cm (Real and inverted

Answer 2

whoa that's big but i will make it easy :)

height of the image = 5cm

u = - 30 cm ( object distance is always minus )

f = - 10 ( focal length of concave mirror is always minus )

using formula

1/f = 1/v + 1/u

we need image that is v so

1/v = 1/f - 1/u

1/v = 1/-10 - 1/-30

1/v = 30 - 10/ -300 = 20/-300

1/v = 1/-15

v = -15 ( cuz in concave mirror image is mostly formed on left side )

therefore the screen should be placed 15 cm away .

type of image is real and inverted

now

magnification = - v/u

15/30 = 1/2 = 0.5

so now

m = height of image / height of object

 0.5 =  5/ height of object

therefore the height of object is 10 cm

the answer is a bit big but if u understood then no probs.