Question

Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
A. A convex lens of focal length $50cm$
B. A concave lens of focal length $50cm$
C. A convex lens of focal length $5cm$
D. A concave lens of focal length $5cm$

Answer 1

Hint: The longer the focal distance, the narrower the angle of view and therefore the higher the magnification. The shorter the focal distance, the broader the angle of view and therefore the lower the magnification. Finding focal distance uses the focal distance formula and requires knowing the space from the first object to the lens u and therefore the distance from the lens to the image v.

Formula used: $\dfrac{1}{f}=\dfrac{1}{u}+\dfrac{1}{v}$
Where:
$f$- focal length
$u$- distance from the original object to lens
$v$- distance from the lens to the image

Complete step by step answer:
A converging lens or convex lens is additionally used as an easy microscope. The thing is kept between the focal distance and mirror in order that a virtual, erect and magnified image is made. Smaller focal distance has more power and is suitable for larger magnification.
Hence, a convex lens of focal distance $5cm$ is preferred.

So, the correct answer is “Option C”.

Additional Information:
An optical lens is usually made from two spherical surfaces. If those surfaces are bent outwards, the lens is named a biconvex lens or just converging lens. These sorts of lenses can converge a beam of sunshine coming from outside and focus it to some extent on the opposite side. now is understood because the focus and therefore the distance between the middle of the lens to the main target is named the focal distance of the converging lens.

Note: Focal length, usually represented in millimetres (mm), is that the basic description of a photographic lens. it's not a measurement of the particular length of a lens. The focal distance of a lens is decided when the lens is concentrated at infinity. Lens focal distance tells us the angle of view—how much of the scene is going to be captured—and the magnification—how large individual elements are going to be.