An object is placed at a distance of 25 cm from the pole of a convex mirror and a plane mirror is set so that the virtual images formed by two mirrors do not have any parallax. The plane mirror is 20 cm from the object. The focal length of the mirror is

Question

An object is placed at a distance of 25 cm from the pole of a convex mirror and a plane mirror is set so that the virtual images formed by two mirrors do not have any parallax. The plane mirror is 20 cm from the object. The focal length of the mirror is (A) 37.5 cm (B) -7.5 cm (C) -37.5 cm (D) +75 cm

Tardigrade Admin · Accepted Answer

For plane mirror, image is formed 20 cm behind it as the object is 20 cm in front of it. For convex mirror, Plane Mirror, <img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/54ee42859012b5968dc1542b54431213-.png" /> (1/f)=(1/v)+(1/u)=(1/15)+(1/-25) ⇒ f=37.5 cm

Q. An object is placed at a distance of $25 c m$ from the pole of a convex mirror and a plane mirror is set so that the virtual images formed by two mirrors do not have any parallax. The plane mirror is $20 c m$ from the object. The focal length of the mirror is

37.5 cm

-7.5 cm

-37.5 cm

+75 cm

For plane mirror, image is formed $20 c m$ behind it as the object is $20 c m$ in front of it. For convex mirror, Plane Mirror,

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u} = \frac{1}{15} + \frac{1}{- 25} \Rightarrow f = 37.5 c m$

Q. An object is placed at a distance of 25cm from the pole of a convex mirror and a plane mirror is set so that the virtual images formed by two mirrors do not have any parallax. The plane mirror is 20cm from the object. The focal length of the mirror is