Refraction Through Lens

How do you say that the focal length of a concave lens is always negative?

An object is placed at a distance $20 \mathrm{cm}$ from a convex lens of focal length $10 \mathrm{cm}$. Select the correct image distance and nature of the image.

The convex lens always gives small virtual image.

What do you mean by focal plane of a lens ?
 

A combination of prisms having a common base behaves like a

The figure below shows a lens treated as a combination of two prisms and a glass block.
(i) Name the lens formed by the combination. (ii) Is the lens converging or diverging?
(iii) Draw the refraction of two incident rays to illustrate the property of the lens mentioned by you in part (ii).
 

The diagram below shows a lens as a combination of a glass block and two prisms. Copy the diagram and answer the following questions:

(i) Name the lens formed by the combination.
(ii) What is the line XY called?
(iii) Complete the ray diagram and show the path of the incident ray AB after passing through the lens.
(iv) The final emergent ray will either meet XY at a point or appear to come from a point on XY. What is the point called?

Draw a diagram to show the divergent action of a diverging lens by treating it as a combination of prisms with the bases away from the centre of the lens.

Draw a diagram to show the convergent action of a converging lens by treating it as a combination of prisms with the bases towards the centre of the lens.

A convex lens is also known as converging lens.

What do you mean by focal plane of a lens ?

What is centre of curvature of a lens?

A _____ (convex / concave) lens can produce both real and virtual images.

At what distance from a convex lens of focal length $24 \mathrm{cm}$, should an object be placed so that the lens forms an image of the same size as the object?

To obtain a magnification of, $-\frac{1}{2}$ with a convex lens, the object should be placed:

When the object is placed between the $f$ and $2f$ of a convex lens, it produces a virtual, erect and magnified image.

Select the correct ray diagram for image formation by concave lens when the object is placed between infinity and optical centre.

The refractive index of convex lens material is $1.46$. The refractive index of benzene and water is $1.5$ and $1.0$ respectively. From the following statements, identify the correct statement which shows the behaviour of the convex lens when it is kept in benzene and water.

Identify from the following the correct statement about the characteristics of the image formed by a convex lens having a focal length of $25 \mathrm{cm}$ when the object is kept on the principal axis at a distance of $50 \mathrm{cm}$ and $75 \mathrm{cm}$.

A bi-convex lens converges the parallel rays on the principal axis at $10 \mathrm{cm}$, then focal length is