A convex lens is put $10cm$ from a light source and it makes a sharp image on a screen, kept $10cm$ from the lens. Now a glass block (refractive index 1.5) of $1.5cm$ thickness is placed in contact with the light source. To get the sharp image again, the screen is shifted by a distance $d$. Then $d$ is :

Q. A convex lens is put $10\text{cm}$ from a light source, and it makes a sharp image on a screen, kept $10\text{cm}$ from the lens. Now a glass block $\text{(refractive index 1.5)}$ of $1.5\text{cm}$ thickness is placed in contact with the light source. To get the sharp image again, the screen is shifted by a distance $d$. Then $d$ is:

Q. A convex lens is put $10\text{cm}$ from a light source and it makes a sharp image on a screen,kept $10\text{cm}$ from the lens. Now a glass book (refractive index $1.5$) of $1.5\text{cm}$ thickness is placed in contact with the light source. To get the sharp image again, the screen is shifted by a distance $d$. Then $d$ is

Q. A convex lens is put $10\text{cm}$ from a light source and it makes a sharp image on a screen, kept $10\text{cm}$ from the lens on its other side. Now a glass block (refractive index $1.5$) of $1.5\text{cm}$ thickness is placed in contact with the light source. To get the sharp image again, the screen must be shifted by a distance $d$. Find the value of $d$.

Q. An object is placed $30cm$ away from a convex lens of focal length $10cm$ and a sharp image is formed on a screen. Now a concave lens is placed in contact with the convex lens. The screen now has to be moved by $45cm$ to get a sharp image again. The magnitude of focal length of the concave lens is (in $cm$):

Q. A converging beam of the light forms a sharp image on a screen. A lens is placed in the path of the beam, the lens being $10cm$ from the screen. It is found that the screen has to be moved $8cm$ further away from the lens to obtain a sharp image. Find the focal length and nature of lens.