The distance between a convex lens and a plan | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(B) When parallel rays are incident on a convex lens,they converge at its focal point at a distance $f$ from the lens.Since the rays are reflected by

Vedclass · Accepted Answer

$20$

Vedclass · Answer

(B) When parallel rays are incident on a convex lens,they converge at its focal point at a distance $f$ from the lens.Since the rays are reflected by a plane mirror placed at a distance of $10 \, cm$ from the lens,the rays appear to come from an object point behind the mirror.According to the property of a plane mirror,the image formed by the mirror is at the same distance behind the mirror as the object is in front of it.Here,the rays are converging towards a point at distance $f$ from the lens. Since the mirror is at $10 \, cm$,the distance of this convergence point from the mirror is $(f - 10) \, cm$.For the rays to form an image at the optical centre of the lens after reflection,the reflected rays must appear to originate from a virtual object located at the optical centre.Thus,the distance of the virtual object from the mirror must be equal to the distance of the image from the mirror.Therefore,$f - 10 = 10$,which gives $f = 20 \, cm$.

The distance between a convex lens and a plane mirror is $10 \, cm$. The parallel rays incident on the convex lens after reflection from the mirror form an image at the optical centre of the lens. The focal length of the lens will be.....$cm$.

Similar Questions

$A$ prism having a refractive index $1.414$ and a refracting angle $30^{\circ}$ has one of its refracting surfaces silvered. $A$ beam of light incident on the other refracting surface will retrace its path if the angle of incidence is: (in $^{\circ}$)

An equiconvex glass lens $(a)$ has a focal length $f$ and power $P$. It is cut into two symmetrical halves $(b)$ by a plane containing the principal axis. The two pieces are recombined as shown in figure $(c)$. The power of the new combination is

$A$ concave mirror of focal length $f_1$ is placed at a distance of $d$ from a convex lens of focal length $f_2$. $A$ beam of light coming from infinity and falling on this convex lens-concave mirror combination returns to infinity. The distance $d$ must equal:

$A$ thin convex lens of focal length $f$ is placed on a plane mirror as shown in the figure. When an object is kept at a distance $a$ from the lens-mirror combination,its image is formed at a distance $a/3$ in front of the combination. The value of $a$ is

$A$ bi-convex lens of focal length $10\,cm$ is cut into two identical parts along a plane perpendicular to the principal axis. The power of each lens after the cut is $...........\,D$.

Vedclass Test Series

Exam Paper Generator

Online Exam Module