Question

When an object is placed 20cm from a concave mirror,a real image magnified three times is formed . Find the focal length of the mirror.Where must the ovject be placed to give a virtual image three times the hight of the object?​plzz answer me fast

Answer 1

QUESTION

When an object is placed 20cm from a concave mirror,a real image magnified three times is formed . Find the focal length of the mirror.Where must the ovject be placed to give a virtual image three times the hight of the object?​

ANSWER

1). Since the magnification Is given

So , m =-3

In this case the image is real

Now coming to object distance denoted by u

U = -20 cm

Now we should find the magnification

So the formula is

✔️✔️ m = -v/u ✔️✔️

Given m = -3

So applying to the formula

-3 = -V/U

Here u =-20 cm

-3= -V/(-20)

By calculating we will get

V = -60 cm

Image is located at a distance of 60 cm Infront of the mirror

✔️✔️ MIRROR FORMULA ✔️✔️

☣ 1/v +1/u =1/f

=> 1/(-60)+1/(-20) =1/f

=> therefore by calculating we will get

F = -15cm

2) m =h2/h1

=> m = -V/U =3

=> v = -3u

✔️✔️ MIRROR FORMULA ✔️✔️ Applying one more time

☣ 1/v + 1/u = 1/f

=> 1/(-3u) +1/u =1/-15

By calculating these terms

We will get the answer as

☣ u = - 10 cm ☣✔️✔️