Refraction by Spherical Lenses

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 -

A person cannot see distinctly objects kept beyond $2 \mathrm{m}$. This defect can be corrected by using a lens of power

A concave lens produces an image $20 \mathrm{cm}$ from the lens of an object placed $30 \mathrm{cm}$ from the lens. The focal length of the lens is:

Given below are a few steps (not in proper sequence) followed in the determination of focal length of a given convex lens by obtaining a sharp image of a distant object—

$\left(A\right)$ Measure the distance between the lens and screen.

$\left(B\right)$ Adjust the position of the lens to form a sharp image.

$\left(C\right)$ Select a suitable distant object.

$\left(D\right)$ Hold the lens between the object and the screen with its faces parallel to the screen.

The correct sequence of steps for determination of focal length is—

If a ray of light passes along the principal axis of a convex lens, it

When a convex lens forms an image whose size is equal to that of the object, the object is placed

A lens may have two spherical surfaces, bulging outwards. Such a lens is called a convex lens. It is thicker at the middle as compared to the edges. A concave lens is bounded by two spherical surfaces, curved inwards. It is thicker at the edges than at the middle. Answer the following question.

The nature of images formed by two lenses are given.
(i) An erect and magnified virtual image
(ii) An erect and diminished virtual image

To get an image having the same size as the object, what is the position of the object?

A lens may have two spherical surfaces, bulging outwards. Such a lens is called a convex lens. It is thicker at the middle as compared to the edges. A concave lens is bounded by two spherical surfaces, curved inwards. It is thicker at the edges than at the middle. Answer the following question.

The nature of images formed by two lenses are given.
(i) An erect and magnified virtual image
(ii) An erect and diminished virtual image

By using which type of lens will we get an image having the same size as the object?

A lens may have two spherical surfaces, bulging outwards. Such a lens is called a convex lens. It is thicker at the middle as compared to the edges. A concave lens is bounded by two spherical surfaces, curved inwards. It is thicker at the edges than at the middle. Answer the following question.

The nature of images formed by two lenses are given.
(i) An erect and magnified virtual image
(ii) An erect and diminished virtual image

What type of lens is used in the second case?

Assertion: Virtual images are always erect.

Reason: Virtual images are formed by diverging lenses only.

What is the centre of the sphere from which the lens is formed called?

An object is placed at infinity with respect to a concave lens of focal length $20 \mathrm{cm}$. The distance of a virtual image from the lens will be

The focal length of a convex lens is $15 \mathrm{cm}$. What should be the object distance to get a real image equal to the size of the object?

The image formed by a pin hole camera is sharpest when the

The nature of the image formed when the object is placed at a distance of twice the focal length from the convex lens is-

Which of the following gives the lens formula?

A $2 \mathrm{cm}$ tall object is placed at a distance of $15 \mathrm{cm}$ from a convex lens of focal length $10 \mathrm{cm}$. Then the image distance is _______

Which is a correct formula for power of a lens?