List of top Physics Questions on Refraction At Spherical Surfaces And By Lenses asked in CBSE Class XII

Depict refraction of a plane wave by a convex lens.
Assertion (A) : When a convex lens made of glass is immersed in water, its converging power increases. Reason (R) : The focal length of a lens depends only on the radii of curvature of its two faces.
A thin plano-convex lens and a thin equi-concave lens are kept coaxially in contact as shown in the figure. Assuming both the lenses are made of glass of refractive index \(\mu\), and \(R\) is the radius of curvature of each curved surface, the focal length of the combination is :

In an experiment with convex lens of focal length f, the screen is fixed at a distance D from the object. A student slowly moves the lens away from the object towards the screen and finds that she is able to form sharp image of the object for two positions of the lens. The distance between these two positions of the lens is d. 

In an experiment with convex lens of focal length f, the screen is fixed at a distance D from the object. A student slowly moves the lens away from the object towards the screen and finds that she is able to form sharp image of the object for two positions of the lens. The distance between these two positions of the lens is d. 

Using the relation for refraction at a curved spherical surface, derive the expression for lens maker's formula.
Three lenses \(L_1\), \(L_2\) and \(L_3\), each of focal length \(40\) cm, are placed coaxially. The distance between \(L_1\) and \(L_2\) and between \(L_2\) and \(L_3\) are \(120\) cm and \(20\) cm respectively. An object is kept at a distance of \(80\) cm to the left of lens \(L_1\). Find the distance of the final image formed from the object.
A concave lens of focal length \(10\) cm is cut into two identical plano-concave lenses. The focal length of each lens will be
Two thin lenses of focal length \(f_1\) and \(f_2\) are placed in contact with each other coaxially. Prove that the focal length \(f\) of the combination is given by \[ f=\frac{f_1f_2}{f_1+f_2}. \]
A point object is kept in front of a convex spherical surface of radius of curvature $R$. Draw the ray diagram to show the formation of image and derive the relation between the object and image distance ($u$ and $v$) in terms of refractive index $n$ of the medium and $R$.
A convex lens of focal length of $20\text{ cm}$ is used to form the image of an object placed $30\text{ cm}$ away from the lens. Find the position and nature of the image formed.
Two thin converging lenses of focal length $f_1$ and $f_2$ are placed coaxially in contact. Derive expression for the focal length of the combination.
Using the relation for refraction at a curved spherical surface, derive the expression for lens maker's formula.
Three lenses \(L_1\), \(L_2\) and \(L_3\), each of focal length \(40\) cm, are placed coaxially. The distance between \(L_1\) and \(L_2\) and between \(L_2\) and \(L_3\) are \(120\) cm and \(20\) cm respectively. An object is kept at a distance of \(80\) cm to the left of lens \(L_1\). Find the distance of the final image formed from the object.
A concave lens of focal length \(10\) cm is cut into two identical plano-concave lenses. The focal length of each lens will be
Two thin lenses of focal length \(f_1\) and \(f_2\) are placed in contact with each other coaxially. Prove that the focal length \(f\) of the combination is given by \[ f=\frac{f_1f_2}{f_1+f_2}. \]
Two thin converging lenses of focal length $f_1$ and $f_2$ are placed coaxially in contact. Derive expression for the focal length of the combination.
A point object is kept in front of a convex spherical surface of radius of curvature $R$. Draw the ray diagram to show the formation of image and derive the relation between the object and image distance ($u$ and $v$) in terms of refractive index $n$ of the medium and $R$.
A convex lens of focal length of $20\text{ cm}$ is used to form the image of an object placed $30\text{ cm}$ away from the lens. Find the position and nature of the image formed.