Refraction by Spherical Lenses

What is focal length?

An object is placed at the following distances from a convex lens of focal length $10 \mathrm{cm}$.
(a) $8 \mathrm{cm}$

(b)$15 \mathrm{cm}$

(c) $20 \mathrm{cm}$

(d) $25 \mathrm{cm}$
Which position of the object will produce
    i. A diminished, real and inverted image?
    ii. A magnified, real and inverted image?
    iii. A magnified, virtual and erect image?
    iv. An image of the same size as object?
Justify your answer in each case.

The following data-was recorded for values of object distance and the corresponding values of image distance in the experiment on study of real image formation by a convex lens of power $+5 \mathrm{D}$.

In a convex lens, when the object is placed at infinity the size of the image formed is _____.

What are the sign convention of a convex and concave lens?

A real inverted image of size of object is to be formed by holding the object at $1 \mathrm{m}$ from a convex lens. What should be the focal length of the lens.

An object of height $20 \mathrm{cm}$ is kept in front of a convex lens and its distance from lens is $80 \mathrm{cm}$. If the focal length is $30 \mathrm{cm}$, calculate the distance of image, its nature, size and magnification.

Differentiate between mirror and lens.

Define and write the lens formula.

Find the power of a convex lens which forms a real inverted image of magnification $-1$ of an object placed at a distance of $20 \mathrm{cm}$ from its optical centre.

A student has to project a three times magnified image of a candle flame on a wall. Name the type of the lens (converging/diverging) required for the purpose.

If the candle flame is at a distance of $6 \mathrm{m}$ from the wall, find the focal length of the lens. 

Complete the ray diagram.

Why is an image through a convex lens used in spectacles does not seems inverted?

Differentiate between mirror and lens.

An object of height $3 \mathrm{cm}$ is placed at $10 \mathrm{cm}$ from a concave lens of focal length $15 \mathrm{cm}$. Select the correct size of the image.

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.

The power of lens depends on the focal length of the lens.

A $2 \mathrm{cm}$ tall object is placed perpendicular to the principal axis of a convex lens of focal length $10 \mathrm{cm}$. The distance of object from the lens is $15 \mathrm{cm}$. Find the position, nature and size of the image. Calculate the magnification of the lens.

An object is put at a distance $25 \mathrm{cm}$ from the optical centre of a convex lens. If its real image is formed at a distance $30 \mathrm{cm}$ from the lens then its focal length is about -