Question

An object is placed in front of a concave mirror at a very far distance.
If the radius of curvature of the mirror is 18 cm, then the image of the
object in front of the mirror will be formed at a distance of

Answer 1

Answer:

Explanation:

When an object is placed at a large distance in front of a concave mirror of a radius of curvature 40 cm, it means the object is at infinity. And, we know that when the object is at infinity then the image is formed at the focus.

Answer 2

Image of the  object in front of the mirror will be formed at a distance of $9cm$.

Explanation:

• Concave mirror is a spherical mirror whose outward surface is painted. Inner surface of the sphere aperture acts as the reflecting surface.
• Light incident on the mirror, gets converged on a point and image is formed.
• Object at a far off distance is considered to be at infinity.
• Rays from an object kept an infinity converges at the focus.
• Focus is a point on principal axis where rays parallel to principal axis and coming from infinity converge.
• Focal length of spherical mirror is half of the radius of curvature.
• Here, focal length is the distance of focus from pole.
• For concave mirror, object at infinity forms an image at focus which is diminished and real i.e. in front of mirror.
• Radius of curvature (given) $=18 cm$
• So, focal length $=\frac{R}{2}=\frac{18}{2}=9cm$

Image is formed at $9 cm$ in front the mirror.