Question

Ello ♥️ Brainlics !!
Question 1. :-
Distinguish Between A Convex Lens and Concave Lens without touching them.
Question 2. :-
Explanation on Power Of Lens.
________
_________Be Brainly !!​

Answer 1

Answer:

Question (1):-Images produced by convex lenses are magnified. Rays of light that pass through a concave lens diverge This means that the rays of light spread outwards and apart from one another. As a result, images produced by concave lenses are diminished.

Difference Between Convex and Concave Lens

convex lens vs concave lensThe lens is understood as a curved and transparent piece of glass or plastic, which focuses and refracts light rays in a certain manner. The curvature of the object ascertains the extent to which light is bent and in which direction. They are used in spectacles, microscope and telescopes. Based on the shape, the lens can be grouped as a convex lens or concave lens. The former brings together the parallel beam of light, while the latter disperses it.

So, the point of focus in case of the convex lens is the point where all the light rays meet, i.e. point of convergence, but if we talk about the concave lens, the focal point is the point from where the light rays seem to diverge, i.e. point of divergence.

Let’s understand the difference between convex and concave lens, with the help of the diagram below.

Questions (2):-Power of lens is the ability of the lens to converge the rays of light falling on it. It can also be defined as P=1/f where f is the focal length. ... One Dioptre is the power of a lens whose focal length is 1 metre. Convex lens has positive power while concave lens has negative power.

SI Unit is Diaopter. (D)

Answer 2

${\boxed{\tt{Distinguishion\:!!}}}$

Between Convex Lens and Concave Lens without Touching

Place the given lens near this book. If the image of the prints appears enlarged, then lens is convex lens and if diminished then the lens is Concave lens.

Uses Of Lens !!

Lenses are used in :-

• Spectacles.
• In Optical instruments like Camera, Microscope, telescope etc.

${\boxed{\tt{Power\:Of\:Lens\:!!}}}$

Power of Lens is its capacity to converge/diverge rays falling on it.

Quantitatively, Power of a lens is the reciprocal of the focal length of the lens.

P(Dioptre) = 1/f(in m)

SI unit :- When f is measured in metre the unit of power is Dioptri(D).

_________________________________

${\boxed{\tt{In\:Extra\:!!}}}$

Definition of Dioptre :- A lens is of power 1 Dioptre when it has a focal length of 1 m.

$1D = 1 {m}^{ - 1}$

$P(Dioptre) = \frac{100}{f(in \: cm)}$

$P(Dioptre) = \frac{1}{f(in \: m)}$

Some Important Conclusions !!

• Focal Length of a converging lens is positive. Therefore, Power of a converging lens is Positive.
• Focal length of a concave lens is negative. Therefore, Power of a concave lens is negative.
• If focal length is small, then the Converging/diverging power of the lens is more and vice - versa .

Note :----

The Power of a Lens can be measured directly by a lens measure Dioptremeter.